5i' PART IV SUPPLEMENTS TO THE SERIES E RECOMMENDATIONS RELATING TO TELEPHONE NETWORK MANAGEMENT AND TRAFFIC ENGINEERING MONTAGE: PAGE PAIRE = PAGE BLANCHE Supplement No. 1 TABLE OF THE ERLANG FORMULA Table of the Erlang loss formula (Erlang No. 1 formula, also called Erlang B formula) Loss probabilities : 1%, 3%, 5%, 7%. Let p = the loss probability y = the traffic offered (in Erlangs) n = the number of cir- cuits -v'2P' -v'3p' Formula: E 1, n (y ) = p = $$2o fIn ! ________ $$3u1 + [Formula Deleted] ! _____ + fIn ! ________ $$3e H.T. [T1.1] Unable to convert table Table 1 [T1.1], p. Supplement No. 2 CURVES SHOWING THE RELATION BETWEEN THE TRAFFIC OFFERED AND THE NUMBER OF CIRCUITS REQUIRED Figure 1, p. Figure 2, p. Supplement No. 3 INFORMATION ON TRAFFIC ROUTING IN THE INTERNATIONAL NETWORK (Results from study in 1973-1976 of Question 11/XIII concerning actual connections of international telephone calls (For the text of this Supplement, see Supplement No. 7, Volume II.2, Orange Book , Geneva, 1976) Supplement No. 4 USE OF COMPUTERS FOR NETWORK PLANNING AND CIRCUIT GROUP DIMENSIONING (For the text of this Supplement, see Supplement No. 8, Volume II.2, Orange Book , Geneva, 1976) Supplement No. 5 TELETRAFFIC IMPLICATIONS FOR INTERNATIONAL SWITCHING AND OPERATIONAL | PROCEDURES RESULTING FROM A FAILURE OF A TRANSMISSION FACILITY 1 Very considerable changes have occurred in the international network over the past decade. These changes have arisen mainly from: - the growth in the number of long-distance routes; - the growth in the number of circuits forming individual long-distance routes; - the world-wide introduction of international automatic operation; - technological developments associated with all aspects of the international network: switching unit design, transmission facility design, and routing and operational stra- tegies; - the integration into the international automatic service of the more isolated geographical areas and of centres hav- ing low-capacity international switching units. 2 The resultant multiplicity of circumstances and situations arising within the international network is now such that it is no longer possible to specify one single criterion for initiating corrective action to counter the loss of a transmission facility. Indeed, the failure of the whole, or part, of a transmission facil- ity may manifest itself in a different manner to each of several Administrations affected by the failure. 3 Among the many aspects of international switching and opera- tional procedures which can influence the degree of curtailment of service arising from a transmission-facility failure, i.e. which can reduce the ability of part of the international network to carry its designed traffic load successfully, the following are specifically stressed (their order has no particular significance): - the introduction of fully automatic interna- tional operation, which means that the control of the network, formerly completely operator -controlled, now depends directly on subscribers' habits; - the number of routes that could be affected by failure and their proportion of the total routes on the switching unit to which they are directly connected: the range can be from one whole route to a few circuits in each of many routes, depending on the method of allocating circuits to transmission facilities; - the influence of any route, for which no alterna- tive transmission facility exists, on the performance of the inter- national switching unit to which it is connected; - the effect on the grade of service of the switch- ing unit itself due to the loss of a complete route or routes, or parts of several routes, directly connected to it; - the methods of limiting the effect of failure on service by action within the switching unit or at preceding inter- national or national switching unit, e.g. by code blocking or recorded announcements; - the cause of the failure, and thus the possible restoration time, relative to the 24-hour traffic profile; - the effect of a failure on overflow and automatic alternative routing strategies ; - the use of diversity of international switching units; - the use of diversity of international transmis- sion facilities. 4 Attention is also drawn to four major factors of maintaining continuity of service: - reliability , - diversity, - network management , and - any redundancy specifically provided to allow restoration of service. 5 Clearly, no practical transmission facility provided will give 100 per cent reliability, so it is inevitable that the other three factors will be involved to varying degrees in maintaining service. The interaction of these four factors will depend largely on the emphasis placed upon each of them by each Administration, thus reinforcing the view that the degree of corrective action that can be taken will depend considerably upon the investment policy (in materials and equipment) and forward-planning objectives of individual Administrations. 6 With respect to diversity, it is recommended that Adminis- trations give consideration to the provision of an adequate number of paths for a particular route, with an adequate level of indepen- dence between the paths. Such independence could reduce the effect of a breakdown or other adverse event by confining it, as far as possible, to only one of the paths used by that route. 7 For the further assistance of Administrations in their study of those teletraffic aspects of international switching and opera- tional procedure which influence the degree of curtailment of service and which arise from a transmission facility failure, these factors are included in Question 23/II related to continuity of service, accepted for study during the 1985-1988 Study Period. Supplement No. 6 TERMS AND DEFINITIONS FOR QUALITY OF SERVICE, NETWORK PERFORMANCE, DEPENDABILITY AND TRAFFICABILITY STUDIES CONTENTS PART I - Dependability Vocabulary 1 Introduction 2 Related Recommendations 3 Basic concepts 4 Performances 5 Events and states 5.1 Defects 5.2 Failures 5.3 Faults 5.4 Errors and mistakes 5.5 States 6 Maintenance 7 Time concepts 7.1 Maintenance related times 7.2 Item state related times 7.3 Time concepts related to reliability perfor- mance 8 Measures of performances 8.1 Availability performance 8.2 Reliability performance 8.3 Maintainability performance 8.4 Maintenance support performance 9 Test, data, design and analysis 9.1 Test concepts 9.2 Data concepts 9.3 Design concepts 9.4 Analysis concepts 9.5 Improvement processes 10 Measure modifiers PART II - Statistical vocabulary 1 Introduction 2 Terms and definitions Annex A: Alphabetical list of definitions contained in this Supplement Annex B: Relations between defect, failure and fault con- cepts Annex C: List of recommended symbols and abbreviations PART I Dependability Vocabulary 1 Introduction A consistent set of terms and definitions is required for the development and use of the various Recommendations addressing aspects relating the specifications, planning, data collection, analysis and evaluation of the dependability, including availabil- ity performance, reliability performance, maintainability perfor- mance and maintenance support performance. These needs address the whole range of operational and maintenance aspects as applicable to telecommunication networks, exchanges, transmission routes and channels, etc., independent of the types of services supported, including aspects of providing the necessary maintenance. The vocabulary provided by this Supplement is also of impor- tance in the handling of concepts related to quality of service and network performance. The conceptual relationships between quality of service and network performance to dependability and other item-related performances is shown in Figure 1. Further information on these performances is found in Recommendation E.800. The vocabulary also provides the necessary linking to the per- formances of components and building blocks (hardware and software) of networks at any level of indenture (ref. definition 6019). Figure 1, p. For the quantitative application and determination of meas- ures, the terms and definitions of Part II also need to be con- sulted. 2 Related Recommendations E.600 - Terms and definitions of traffic engineering E.800 - Quality of service and dependability vocabulary. 3 Basic concepts 3001 item; entity F: entite; individu S: elemento; entidad; item Any part, device, subsystem, functional unit, equipment or system that can be individually considered. Note 1 - An item | ay consist of hardware, software or both, and may also include people, e.g. operators in a telephone operator system. Note 2 - In French, the term entite | eplaces the term dispositif | reviously used in this meaning, because the term dispositif is also the common equivalent for the English term "dev- ice". Note 3 - In French, the term individu | s used mainly in statistics. 3002 repaired item F: entite reparee S: elemento reparado A repairable item | hich is in fact repaired after a failure . 3003 non-repaired item F: entite non reparee S: elemento no reparado An item | hich is not repaired after a failure . Note - A non-repaired item | ay be repairable or not. 3005 required function F: fonction requise S: funcion requerida A function or a combination of functions of an item | hich is considered necessary for the provisioning of a given service . 3006 functional mode F: mode de fonctionnement S: modo de funcionamiento A subset of the whole set of possible functions of an item . 3007 instant of time F: instant S: instante (de tiempo) A single point on a time scale. Note - The time scale may be continuous as calendar time, or discrete, e.g. number of use cycles. 3008 time interval F: intervalle de temps S: intervalo de tiempo All instants of time | etween two given instants of time . 3009 (time) duration F: duree S: duracion The difference between the end points of a time interval . 3010 accumulated time F: duree cumulee S: tiempo acumulado The sum of time durations | haracterized by given conditions over a given time interval . 3011 measure (as applied in the study of reliability per- formance and related areas) F: caracteristique (probabilite); mesure (en fiabilite et domaines connexes) S: medida (aplicada en estudios de fiabilidad y de aspectos conexos) A function or quantity used to describe a random variable | r a random process . Note - For a random variable , examples of measures | re the distribution function | nd the mean . 3012 operation F: exploitation S: explotacion; operacion Combination of all technical and corresponding administrative actions intended to allow an item | to perform a required function , recognizing necessary adaptation to changes in external condi- tions. Note - By external conditions are understood, for example, service demand and environmental conditions. 3013 modification (of an item) F: modification (d'une entite) S: modificacion (de un elemento) The combination of all technical and corresponding administra- tive actions intended to alter the capability of an item by chang- ing, adding or deleting one or more required functions . 4 Performances 4001 dependability F: s | rete de fonctionnement S: seguridad de funcionamiento The collective term used to describe the availability perfor- mance | nd its influencing factors: reliability performance, main- tainability performance and maintenance support performance . Note - Dependability is used only for general descriptions in non-quantitative terms. 4002 availability performance F: disponibilite S: disponibilidad The ability of an item | o be in a state to perform a required function | t a given instant of time or at any instant of time within a given time interval , assuming that the external resources, if required, are provided. Note 1 - This ability depends on the combined aspects of the reliability performance , the maintainability performance and the maintenance support performance of an item . Note 2 - In the definition of the item | he external resources required must be delineated. Note 3 - The term availability | s used as an availability performance measure . Note 4 - Warning: the term availability has occasionally been used in connection with the term item , but with an implied meaning of item being entirely different from that of this Supplement. 4003 reliability performance F: fiabilite S: fiabilidad The ability of an item | o perform a required function | nder given conditions for a given time interval . Note 1 - It is generally assumed that the item | s in a state to perform this required function at the beginning of the time interval . Note 2 - The term reliability | s used as a measure of reli- ability performance . 4004 maintainability performance F: maintenabilite S: mantenibilidad The ability of an item | nder stated conditions of use, to be retained in, or restored to, a state in which it can perform a required function , when maintenance is performed under given condi- tions and using stated procedures and resources. Note - The term maintainability | s used as a measure | f maintainability performance . 4005 maintenance support performance F: logistique de maintenance S: logistica de mantenimiento The ability of a maintenance organization, under given condi- tions, to provide upon demand the resources required to maintain an item , under a given maintenance policy . Note - The given conditions are related to the item | tself and to the conditions under which the item is used and maintained. 4006 durability F: durabilite S: durabilidad The ability of an item | o remain in a condition where it can perform a required function under stated conditions of use and maintenance until a limiting state is reached. Note - A limiting state of an item | ay be characterized by the end of the useful life , unsuitability for any economic or technological reasons, etc. 5 Events and states 5.1 Defects 5101 defect F: defaut S: defecto Any departure of a characteristic of an item | rom require- ments. Note 1 - The requirements may or may not be expressed in the form of a specification. Note 2 - A defect may or may not affect the ability of an item | o perform a required function . 5102 bug F: erreur de programmation; bogue S: error de programacion A software defect | aused by a mistake . 5103 critical defect F: defaut critique S: defecto critico A defect | hat is assessed likely to result in injury to per- sons or significant material damage. 5104 non-critical defect F: defaut non critique S: defecto no critico A defect | ther than a critical defect . 5105 major defect F: defaut majeur S: defecto mayor A defect | hat is likely to result in a failure | r to reduce materially the usability of the item for its intended pur- pose. 5106 minor defect; imperfection F: defaut mineur; imperfection S: defecto menor; imperfeccion A defect other than a major defect . 5107 defective; defective item F: defectueux; entite defectueuse S: defectuoso; elemento defectuoso An item | hich contains one or more defects . 5108 critical defective item F: defectueux critique S: elemento defectuoso critico An item | hich contains one or more critical defect . 5109 major defective item F: defectueux majeur S: elemento defectuoso mayor An item | which contains one or more major defects . 5110 minor defective item F: defectueux mineur S: elemento defectuoso menor An item | hich contains one or more minor defects | ut no major defects . 5111 design defect F: defaut de conception S: defecto de dise~o A defect | ue to an inadequate design of an item . 5112 manufacturing defect F: defaut de fabrication S: defecto de fabricacion A defect | ue to nonconformance in manufacture to the design of an item or to specified manufacturing processes. 5.2 Failures 5201 failure F: defaillance S: fallo The termination of the ability of an item | o perform a required function . Note - After failure | he item | as a fault. 5202 critical failure F: defaillance critique S: fallo critico A failure | hich is assessed likely to result in injury to persons or significant material damage. 5203 non-critical failure F: defaillance non critique S: fallo no critico A failure | ther than a critical failure . 5204 misuse failure F: defaillance par mauvaise utilisation S: fallo por uso incorrecto A failure | ue to induced stresses during use which are beyond the stated capabilities of the item . 5205 mishandling failure F: defaillance par fausse manoeuvre S: fallo por manejo incorrecto A failure | aused by incorrect handling or lack of care of the item 5206 (inherent) weakness failure F: defaillance par fragilite (inherente) S: fallo por fragilidad (inherente) A failure | ue to a weakness inherent in the item | tself when subjected to stresses within the stated capabilities of the item 5207 design failure F: defaillance de conception S: fallo de dise~o A failure | ue to a design defect . 5208 manufacturing failure F: defaillance de fabrication S: fallo de fabricacion A failure | ue to a manufacturing defect . 5209 ageing failure; wearout failure F: defaillance par vieillissement; defaillance par usure S: fallo por envejecimiento; fallo por desgaste A failure | hose probability of occurrence increases with the passage of time, as a result of processes inherent in the item . 5210 sudden failure F: defaillance soudaine S: fallo repentino A failure | hat could not be anticipated by prior examination or monitoring. 5211 gradual failure; degradation failure; drift failure F: defaillance progressive; degradation; defaillance par derive S: fallo gradual; fallo por degradacion; fallo por deriva A failure | ue to a gradual change in time of given charac- teristics of an item and that could be anticipated by prior exami- nation or monitoring. Note - A gradual failure | an sometimes be avoided by preventive maintenance . 5212 cataleptic failure; catastrophic failure (deprecated) F: defaillance cataleptique S: fallo cataleptico; fallo catastrofico | (desacon- sejado) A sudden failure | hich results in a complete fault . 5213 relevant failure F: defaillance pertinente; defaillance a prendre en compte S: fallo pertinente; fallo relevante A failure | o be included in interpreting test or operational results or in calculating the value of a reliability performance measure . Note - The criteria for the inclusion should be stated. 5214 non-relevant failure F: defaillance non pertinente; defaillance a ne pas prendre en compte S: fallo no pertinente; fallo irrelevante A failure | o be excluded in interpreting test or operational results or in calculating the value of a reliability performance measure Note - The criteria for the exclusion should be stated. 5215 primary failure F: defaillance primaire S: fallo primario A failure | f an item , not caused either directly or indirectly by the failure or the fault of another item . 5216 secondary failure F: defaillance secondaire S: fallo secundario A failure | f an item , caused either directly or indirectly by the failure | r the fault of another item . 5217 failure cause F: cause de defaillance S: causa de fallo The circumstances during design, manufacture or use which have led to a failure . 5218 failure mechanism F: mecanisme de defaillance S: mecanismo de fallo The physical, chemical or other process which has led to a failure . 5219 systematic failure; reproducible failure; determinis- tic failure F: defaillance systematique; defaillance reproductible S: fallo sistematico; fallo reproducible; fallo deterministico A failure | elated in a deterministic way to a certain cause, which can only be eliminated by a modification of the design or manufacturing process, operational procedures, documentation or other relevant factors. Note 1 - Corrective maintenance | ithout modification will usually not eliminate the failure cause . Note 2 - A systematic failure | an be induced at will by simulating the failure cause . 5.3 Faults 5301 fault F: panne; derangement S: averia The inability of an item | o perform a required function , excluding that inability due to preventive maintenance , lack of external resources or planned actions. Note - A fault | s often the result of a failure | f the item itself, but may exist without prior failure . 5302 critical fault F: panne critique S: averia critica A fault | hich is assessed likely to result in injury to per- sons or significant damage to material. 5303 non-critical fault F: panne non critique S: averia no critica A fault , other than a critical fault . 5304 major fault F: panne majeure S: averia mayor A fault | hich affects a function considered to be of major importance. 5305 minor fault F: panne mineure S: averia menor A fault | ther than a major fault . 5306 misuse fault F: panne par mauvaise utilisation S: averia por uso incorrecto A fault | ue to induced stresses during use which are beyond the stated capabilities of the item . 5307 mishandling fault F: panne par fausse manoeuvre S: averia por manejo incorrecto A fault | aused by incorrect handling or lack of care of the item . 5308 (inherent) weakness fault F: panne par fragilite (inherente) S: averia por fragilidad (inherente) A fault | ue to a weakness inherent in the item | tself when subjected to stresses within the stated capabilities of the item 5309 design fault F: panne de conception S: averia de dise~o A fault | ue to a design defect . 5310 manufacturing fault F: panne de fabrication S: averia de fabricacion A fault | ue to a manufacturing defect . 5311 ageing fault; wearout fault F: panne par vieillissement; panne par usure S: averia por envejecimiento; averia por desgaste A fault | esulting from an ageing failure . 5312 programme-sensitive fault F: panne mise en evidence par le programme S: averia dependiente del programa A fault | hat is revealed as a result of the execution of some particular sequence of instructions. 5313 data-sensitive fault F: panne mise en evidence par les donnees S: averia dependiente de los datos A fault | hat is revealed as a result of the processing of a particular pattern of data. 5314 complete fault; function preventing fault F: panne complete S: averia completa A fault | haracterized by complete inability to perform all required functions of an item . Note - The criteria for a complete fault | ave to be stated. 5315 partial fault F: panne partielle S: averia parcial A fault | f an item | ther than a complete fault . 5316 persistent fault; permanent fault; solid fault F: panne permanente S: averia permanente A fault | f an item | hat persists until an action of corrective maintenance is performed. 5317 intermittent fault; volatile fault; transient fault F: panne intermittente; panne temporaire S: averia intermitente; averia transitoria A fault of an item | hich persists for a limited time dura- tion | ollowing which the item recovers the ability to perform a required function without being subjected to any action of corrective maintenance Note - Such a fault is often recurrent. 5318 determinate fault F: panne franche S: averia clara; averia determinable For an item , which produces a response as a result of an action, a fault for which the response is the same for all actions. 5319 indeterminate fault F: panne indeterminee S: averia indeterminable For an item , which produces a response as a result of an action, a fault such that the error affecting the response depends on the action applied. Note - An example would be a data-sensitive fault . 5320 latent fault F: panne latente S: averia latente An existing fault | hat has not yet been recognized. 5321 systematic fault F: panne systematique S: averia sistematica A fault | esulting from a systematic failure . 5322 fault mode; failure mode (deprecated) F: mode de panne; mode de defaillance | (terme deconseille) S: modo de averia; modo de fallo | (desaconsejado) One of the possible states of a faulty item , for a given required function . 5323 faulty F: en panne S: averiado Property of having a fault . 5.4 Errors and mistakes 5401 error F: erreur S: error A discrepancy between a computed, observed or measured value or condition and the true, specified or theoretically correct value or condition. Note - An error | an be caused by a faulty item , e.g. a computing error | ade by a faulty computer equipment. 5402 execution error; generated error F: erreur d'execution S: error de ejecucion Error | roduced during the operation of a faulty item . 5403 interaction error (man-machine) F: erreur d'interaction | (homme-machine) S: error de interaccion | (hombre-maquina) An error | n the response of an item | aused by a mistake | uring its use. 5404 propagated error F: erreur propagee S: error propagado An error | n the response to erroneous data input to a non-faulty item . 5405 mistake; error (deprecated in this sense) F: erreur (humaine); faute S: equivocacion; error | (desaconsejado en este sen- tido) A human action that produces an unintended result. 5.5 Item related states | see also Figure 2) Figure 2, p. 5501 operating state F: (etat de) fonctionnement S: estado de funcionamiento; estado operacional The state when an item | s performing a required function . 5502 non-operating state F: (etat de) non-fonctionnement S: estado de no funcionamiento The state when an item | s not performing a required function . 5503 standby state F: (etat d') attente S: estado de espera (en reserva) A non-operating up state | uring the required time . 5504 idle state; free state F: etat vacant; etat libre S: estado de reposo; estado libre A non-operating up state | uring non-required time . 5505 disabled state; outage F: etat d'incapicite S: estado de incapacidad A state of an item | haracterized by its inability to per- form a required function , for any reason. 5506 external disabled state F: etat d'incapacite externe S: estado de incapacidad externa That subset of the disabled state | hen the item | s in an up state , but lacks required external resources. 5507 down state; internal disabled state F: etat d'indisponibilite; etat d'incapacite interne S: estado de indisponibilidad; estado de incapacidad interna A state of an item | haracterized by a fault | r by a possi- ble inability to perform a required function during preventive maintenance . Note - This state relates to availability performance . 5508 up state F: etat de disponibilite S: estado de disponibilidad A state of an item | haracterized by the fact that it can perform a required function , assuming that the external resources, if required, are provided. Note - This state relates to availability performance . 5509 busy state F: etat occupe; occupation S: estado de ocupacion; estado de ocupado The state of an item | n which it performs a required func- tion | or a user and for that reason is not accessible by other users. 5510 critical state F: etat critique S: estado critico A state of an item | ssessed likely to result in injury to persons or significant material damage. Note - A critical state | ay be the result of a critical fault , but not necessarily. 6 Maintenance 6001 maintenance philosophy F: philosophie de maintenance S: filosofia de mantenimiento A system of underlying principles for the organization and execution of the maintenance . 6002 maintenance policy F: politique de maintenance S: politica de mantenimiento A description of the interrelationship between the maintenance echelons , the indenture levels and the levels of maintenance to be applied for the maintenance of an item . 6003 maintenance F: maintenance S: mantenimiento The combination of all technical and corresponding administra- tive actions, including supervision actions, intended to retain an item in, or restore it to, a state in which it can perform a required function . 6004 preventive maintenance F: maintenance preventive; entretien S: mantenimiento preventivo The maintenance | arried out at predetermined intervals or according to prescribed criteria and intended to reduce the proba- bility of failure or the degradation of the functioning of an item . 6005 corrective maintenance; repair F: maintenance corrective; reparation; depannage S: mantenimiento correctivo; reparacion The maintenance | arried out after fault recognition | nd intended to restore an item to a state in which it can perform a required function . 6006 deferred maintenance F: maintenance differee S: mantenimiento diferido Such corrective maintenance | hich is not immediately ini- tiated after a fault recognition but is delayed in accordance with given maintenance rules. 6007 scheduled maintenance F: maintenance programmee; entretien systematique S: mantenimiento programado The preventive maintenance | arried out in accordance with an established time schedule. 6008 unscheduled maintenance F: maintenance non programmee S: mantenimiento no programado The maintenance | arried out, not in accordance with an esta- blished time schedule, but, for example, after reception of an indication regarding the state of an item . 6009 on-site maintenance; in situ maintenance; field maintenance F: maintenance in situ S: mantenimiento local; mantenimiento sobre el terreno Maintenance | erformed at the premises where the item | s used. 6010 off-site maintenance F: maintenance deportee S: mantenimiento no local Maintenance | erformed at a place different from where the item is used. Note - An example is the repair | f a sub-item at a mainte- nance centre. 6011 remote maintenance F: telemaintenance S: mantenimiento remoto; telemantenimiento Maintenance | f an item | erformed without physical access of the personnel to the item . 6012 automatic maintenance F: maintenance automatique S: mantenimiento automatico Maintenance | ccomplished without human intervention. 6013 function-affecting maintenance F: maintenance affectant les fonctions S: mantenimiento que afecta a la funcion A maintenance action | hat affects one or more of the required functions of a maintained item . Note - Function-affecting maintenance | s divided into function-preventing maintenance and function-degrading maintenance . 6014 function-preventing maintenance F: maintenance-arr | t; maintenance emp | chant l'accomplissement des fonctions S: mantenimiento con discontinuidad de funciones A maintenance action | hat prevents a maintained item | rom performing a required function by causing complete loss of all the functions. 6015 function-degrading maintenance F: maintenance avec degradation; maintenance degradant les fonctions S: mantenimiento con degradacion de funciones A maintenance action | hat affects one or more of the required functions | f a maintained item , but not to such extent as to cause complete loss of all the functions. 6016 function-permitting maintenance F: maintenance en fonctionnement; maintenance en exploitation S: mantenimiento sin discontinuidad de funciones A maintenance action | hat does not affect any of the required functions | f a maintained item . 6017 level of maintenance F: niveau de maintenance S: nivel de mantenimiento The maintenance action | o be carried out at a specified indenture level . Note - Examples of a maintenance action | re replacing a component, a printed circuit board, a subsystem, etc. 6018 maintenance echelon; line of maintenance F: echelon de maintenance S: escalon de mantenimiento; linea de mantenimiento The position in an organization where specified levels of maintenance | re to be carried out on an item . Note 1 - Examples of maintenance echelons | re: field, repair shop, manufacturer. Note 2 - The maintenance echelon | s characterized by the skill of the personnel, the facilities available, the location, etc. 6019 indenture level (for maintenance) F: niveau d'intervention (pour la maintenance) S: nivel de intervencion (para el mantenimiento) A level of subdivision of an item | rom the point of view of a maintenance action . Note 1 - Examples of indenture levels | ould be a subsystem, a circuit board, a component. Note 2 - The indenture level | epends on the complexity of the item's construction, the accessibility to sub-items, skill level of maintenance personnel, test equipment facilities, safety considerations, etc. 6020 elementary maintenance activity F: operation elementaire de maintenance S: accion elemental de mantenimiento The unit of work into which a maintenance activity may be bro- ken down at a given indenture level . 6021 maintenance action; maintenance task F: operation de maintenance; t | che de maintenance S: accion de mantenimiento; tarea de mantenimiento A sequence of elementary maintenance activities | arried out for a given purpose. Note - Examples are fault diagnosis , fault localization | nd function check-out or combinations thereof. 6022 supervision F: surveillance; supervision S: supervision Activity, performed either manually or automatically, intended to observe the state of an item . Note - Automatic supervision | ay be performed internally or externally to the item . 6023 controlled maintenance F: maintenance dirigee S: mantenimiento dirigido A method to sustain a desired quality of service | y the sys- tematic application of analysis techniques using centralized super- visory facilities and/or sampling to minimize preventive mainte- nance and to reduce corrective maintenance . 6024 fault recognition F: detection (de panne) S: deteccion (de una averia ) The event when a fault | s recognized. 6025 fault diagnosis F: diagnostic (de panne) S: diagnostico (de una averia) Actions taken for fault recognition , fault localization | nd cause identification. 6026 fault localization; fault location (deprecated in this sense) F: localisation de panne S: localizacion (de una averia) Actions taken to identify the faulty sub-item or sub-items at the appropriate indenture level . 6027 fault correction F: correction (de panne) S: correccion (de una averia) Actions taken after fault localization | ntended to restore the ability of the faulty item to perform a required function . 6028 function check-out F: verification (de fonctionnement) S: verificacion de funcionamiento Actions taken after fault correction | o verify that the item | as recovered its ability to perform the required function . 6029 restoration; recovery F: retablissement S: restablecimiento; restauracion That event when the item | egains the ability to perform a required function after a fault . 6030 maintenance entity F: cellule de maintenance S: cellula de mantenimiento; entidad de mantenimiento A sub-item of a given item | efined with the intention that an alarm - caused by a fault in that sub-item - will be unambigu- ously referrable to the sub-item. 7 Time concepts (see also Figure 3) 7.1 Maintenance related times 7101 maintenance time F: temps de maintenance S: tiempo de mantenimiento The time interval | uring which a maintenance action | s performed on an item either manually or automatically, including technical delays and logistic delays . Note - Maintenance | ay be carried out while the item | s performing a required function . 7102 maintenance man-hours (MMH) F: duree equivalente de maintenance S: duracion equivalente de mantenimiento; horas-hombre de mantenimiento The accumulated durations of the maintenance times , expressed in hours, used by all maintenance personnel for a given type of maintenance action or over a given time interval . Figure 3, p. 6 7103 active maintenance time F: temps de maintenance active S: tiempo de mantenimiento activo That part of the maintenance time | uring which a maintenance action | s performed on an item , either automatically or manu- ally, excluding logistic delays . Note - Active maintenance may be carried out while the item | s performing a required function . 7104 preventive maintenance time F: temps de maintenance preventive S: tiempo de mantenimiento preventivo That part of the maintenance time | uring which preventive maintenance | s performed on an item , including technical delays and logistic delays inherent in preventive maintenance . 7105 repair time; corrective maintenance time F: temps de reparation; temps de maintenance correc- tive S: tiempo de reparacion; tiempo de mantenimiento correctivo That part of the maintenance time | uring which corrective maintenance | s performed on an item , including technical delays and logistic delays inherent in corrective maintenance . 7106 active preventive maintenance time F: temps de maintenance preventive active S: tiempo de mantenimiento preventivo activo That part of the active maintenance time | uring which actions of preventive maintenance are performed on an item . 7107 active repair time; active corrective maintenance time F: temps de reparation active; temps de maintenance corrective active S: tiempo de reparacion activo; tiempo de manten- imiento correctivo activo That part of the active maintenance time | uring which actions of corrective maintenance are performed on an item . 7108 undetected fault time F: temps de non-detection de panne S: tiempo de no deteccion de una averia The time interval | etween a failure | nd recognition of the resulting fault . 7109 administrative delay (for corrective maintenance) F: delai administratif (pour la maintenance correc- tive) S: retardo administrativo (para el mantenimiento correctivo); demora administrativa The accumulated time | uring which an action of corrective maintenance | n a faulty item is not performed due to administra- tive reasons. 7110 logistic delay F: delai logistique S: retardo logistico; demora logistica That accumulated time | uring which a maintenance action | annot be performed due to the necessity to acquire maintenance resources, excluding any administrative delay . Note - Logistic delays | an be due to, e.g. travelling to unattended installations, awaiting the arrival of spare parts, spe- cialists or test equipment. 7111 fault correction time F: temps de correction de panne S: tiempo de correccion de una averia That part of active repair time | uring which fault correc- tion | s performed. 7112 technical delay F: delai technique S: retardo tecnico; demora tecnica The accumulated time | ecessary to perform auxiliary techni- cal actions associated with the maintenance action itself. 7113 check-out time F: temps de verification (du fonctionnement) S: tiempo de verificacion (de funcionamiento) That part of active repair time | uring which function check-out | s performed. 7114 fault localization time; fault location time (depre- cated) F: temps de localisation (de panne) S: tiempo de localizacion de una averia That part of active repair time | uring which fault localiza- tion | s performed. 7.2 Item-state related times 7201 operating time F: temps de fonctionnement S: tiempo de funcionamiento The time interval | uring which an item | s an operating state . 7202 non-operating time F: temps de non-fonctionnement S: tiempo de no funcionamiento The time interval | uring which an item | s in a non-operating state . 7203 required time F: periode requise S: periodo requerido The time interval | uring which the user requires the item | o be in a condition to perform a required function . 7204 non-required time F: periode non requise S: periodo no requerido The time interval | uring which the user does not require the item | o be in a condition to perform a required function . 7205 stand-by time F: periode d'attente S: tiempo de espera (en reserva) The time interval | uring which an item | s in a stand-by state . 7206 idle time; free time F: periode vacante; temps mort; temps libre S: tiempo de reposo; tiempo muerto; tiempo libre The time interval | uring which an item | s in a free state . 7207 disabled time F: temps d'incapacite S: tiempo de incapacidad The time interval | uring which an item | s in a disabled state . 7208 down time F: temps d'indisponibilite S: tiempo de indisponibilidad The time interval | uring which an item | s in a down state . 7209 accumulated down time F: duree cumulee d'indisponibilite S: tiempo de indisponibilidad acumulado The sum of the duration of down times | ver a given time interval . 7210 external disabled time; external loss time F: temps d'incapacite externe S: tiempo de incapacidad externa The time interval | uring which an item | s in an external disabled state . 7211 up time F: temps de disponibilite; temps de bon fonctionnement S: tiempo de disponibilidad The time interval | uring which an item | s in an up state . 7.3 Time concepts related to reliability performance 7301 time to first failure F: duree de fonctionnement avant la premiere defaillance S: tiempo hasta el primer fallo Total time duration | f the operating time | f an item | rom the instant of time it is first put in an up state , until failure . 7302 time to failure F: duree de fonctionnement avant defaillance S: tiempo hasta el fallo Total time duration | f the operating time | f an item , from the instant of time it goes from a down state to an up state , after a corrective maintenance action , until the next failure . 7303 time between failures F: temps entre defaillances S: tiempo entre fallos The time duration | etween two successive failures | f a repaired item . Note 1 - Those parts of non-operating time | hich are included must be identified. Note 2 - In some applications only the up time | s con- sidered. 7304 time to restoration; time to recovery F: temps de panne S: tiempo de averia The time interval | uring which an item | s in a down state | ue to a failure . 7305 useful life F: (duree de) vie utile S: vida util Under given conditions, the time interval | eginning at a given instant of time , and ending when the failure intensity becomes unacceptable or when the item is considered unrepairable as a result of a fault . 7306 early failure period F: periode initiale de defaillance S: periodo de fallos inicial That possible early period in the life of an item , beginning at a given instant of time and during which the instantaneous failure intensity for a repaired item or the instantaneous failure rate for a non-repaired item decreases rapidly. Note - In any particular case, it is necessary to explain what is meant by "decreases rapidly". 7307 constant failure intensity period F: periode d'intensite constante de defaillance S: periodo de intensidad de fallos constante That possible period in the life of a repaired item | uring which the failure intensity is approximately constant. Note - In any particular case it is necessary to explain what is meant by "approximately constant". 7308 constant failure rate period F: periode de densite constante de defaillance; periode de taux constant de defaillance S: periodo de tasa de fallos constante That possible period in the life of a non-repaired item | uring which the failure rate is approximately constant. Note - In any particular case it is necessary to explain what is meant by "approximately constant". 7309 wear-out failure period F: periode de defaillance par vieillissement; periode de defaillance par usure S: periodo de fallos por envejecimiento That possible later period in the life of an item | uring which the instantaneous failure intensity for a repaired item or the instantaneous failure rate for a non-repaired item increases rapidly. Note - In any particular case it is necessary to explain what is meant by "increases rapidly". 8 Measures of performances 8.1 Availability performance 8101 instantaneous availability; pointwise availability; A(t) (symbol) F: disponibilite (instantanee), A(t) | symbole) S: disponibilidad instantanea, A(t) | simbolo) The probability | hat an item | s in an up state | t a given instant of time , t . Note - In French the term disponibilite | s also used to denote the performance quantified by this probability . 8102 instantaneous unavailability; pointwise unavailabil- ity; U(t) (symbol) F: indisponibilite (instantanee), U(t) | symbole) S: indisponibilidad instantanea, U(t) | simbolo) The probability that an item | s in a down state | t a given instant of time , t . 8103 mean availability, A (tv1, | v2) (symbol) F: disponibilite moyenne, A | (t1, t2) (symbole) S: disponibilidad media, A | (t1, t2) (simbolo) The normalized integral of the instantaneous availability | n a given time interval (t1, t2). Note - The mean availability | s related to the instantane- ous availability as A | fR (t 1 , t 2) = [Formula Deleted] t 1 fIt 2 A (t ) dt . 8104 mean unavailability, U (tv1, tv2) (symbol) F: indisponibilite moyenne, U | (t1, | fIt2) (sym- bole) S: indisponibilidad media, U | (t1, | fIt2) (simbolo) The normalized integral of the instantaneous unavailability | n a stated time interval (t1, | fIt2). Note - The mean unavailability | s related to the instan- taneous unavailability as U | fR (t 1 , t 2) = [Formula Deleted] t 1 fIt 2 U (t ) dt . 8105 (asymptotic) availability; (steady-state) availabil- ity; A (symbol) F: disponibilite asymptotique; disponibilite, A | symbole) S: disponibilidad (asintotica); disponibilidad (en regimen permanente); A | simbolo) The limit, if this exists, of the instantaneous availability | hen the time tends to infinity. Note - Under certain conditions, for instance constant failure rate and constant repair rate, the asymptotic availability may be expressed as: A = fIMUT + MDT ___________ where MDT | s the mean down time MUT | s the mean up time . 8106 asymptotic unavailability, U (symbol) F: indisponibilite asymptotique, U | symbole) S: indisponibilidad asintotica, U | simbolo) The limit, if this exists, of the instantaneous unavailability | hen the time tends to infinity. Note - Under certain conditions, for instance constant failure rate and constant repair rate, the asymptotic unavailabil- ity may be expressed as: U = fIMDT + MUT ___________ where MDT | s the mean down time MUT | s the mean up time . 8107 asymptotic mean availability, A (symbol) F: disponibilite moyenne asymptotique, A | (symbole) S: disponibilidad media asintotica, A | (simbolo) The limit, if this exists, of the mean availability | ver a time interval (t1, | fIt2) when t2tends to infinity. Note 1 - The asymptotic mean availability | s related to the mean availability as A | fR = lim A | fR (t 1, t 2) A | fR = t 2 oo Note 2 - When such a limit exists it is not dependent on t1. 8108 asymptotic mean unavailability, U (symbol) F: indisponibilite moyenne asymptotique, U | (sym- bole) S: indisponibilidad media asintotica , U | (simbolo) The limit, if this exists, of the mean unavailability | ver a time interval | t1, | fIt2) when t2tends to infinity. Note 1 - The asymptotic mean unavailability | s related to the mean unavailability | s U | fR = lim U | fR (t 1, t 2) U | fR = t 2 oo Note 2 - When such a limit exists it is not dependent on t1. 8109 mean up time (MUT) F: temps moyen de disponibilite; duree moyenne de disponibilite (TMD) S: tiempo medio de disponibilidad (TMD) The expectation | f the up time . 8110 mean accumulated down time (MADT) F: duree cumulee moyenne d'indisponibilite S: tiempo medio acumulado de indisponibilidad (TMAI) The expectation | f the accumulated down time . 8111 instantaneous availability of a leased circuit F: disponibilite instantanee d'un circuit loue S: disponibilidad instantanea de un circuito arrendado The probability | hat, under stated operating conditions, a leased circuit can perform a required function when requested by the subscriber. 8.2 Reliability performance 8201 reliability, R (symbol) F: fiabilite, R | symbole) S: fiabilidad, R | simbolo) The probability | hat an item | an perform a required func- tion | nder stated conditions for a given time interval . Note 1 - It is generally assumed that the item | s in a state to perform this required function at the beginning of the time interval . Note 2 - In French, the term fiabilite | s also used to denote the performance quantified by this probability . 8202 (instantaneous) failure rate, \(t) (symbol) F: densite (temporelle) (instantanee) de defaillance; taux (instantane) de defaillance, \(t) | (symbole) S: tasa (instantanea) de fallos, \(t) | simbolo) The limit, if this exists, of the ratio of the conditional probability | hat the time to failure , T , of an item falls within a given time interval , (t , | fIt +?63t ), to the length of this interval, ?63t , when ?63t tends to zero, given that the item is in a state to perform a required function at the beginning of the time interval . Note - The instantaneous failure rate | s expressed by for- mula as: \ (t ) = lim \ (t ) = ?63 (t ) 0+ 63t ____________________________ where T | s the instant of time | f failure . The formula is also applicable if T | enotes the time to failure . 8203 mean failure rate, \ (tv1, | v2) (symbol) F: taux moyen de defaillance; densite (temporelle) moyenne de defaillance, \ | (t1, | fIt2) (symbole) S: tasa media de fallos, \ | (t1, | fIt2) (simbolo) The normalized integral of the instantaneous failure rate | ver a given time interval , (t1, | fIt2). Note - The mean failure rate | elates to instantaneous failure rate as \ (t 1 , t 2) = [Formula Deleted] t 1 fIt 2 \ (t ) dt . 8204 (instantaneous) failure intensity, z(t) (symbol) F: intensite (instantanee) de defaillance, z(t) | (symbole) S: intensitad (instantanea) de fallos, z(t) | (simbolo) The limit, if this exists, of the ratio of the mean number of failures | f a repaired item in a time interval , (t , | fIt | | 63t ), to the length of this interval, ?63t , when the length of the time interval tends to zero. Note - The instantaneous failure intensity | s expressed by formula as: z (t ) = lim z (t ) = ?63t 0+ 63t _______________________ where N | t ) is the number of failures | n the time interval | (0, | fIt ). 8205 mean failure intensity, z (tv1, | v2) (symbol) F: intensite moyenne de defaillance, z | (t1, | fIt2) (symbole) S: intensidad media de fallos, z | (t1, | fIt2) (simbolo) The normalized integral of the instantaneous failure intensity | over a given time interval | (t1, | fIt2). Note - The mean failure intensity | s related to instantane- ous failure intensity as: z | fR (t 1 , t 2) = [Formula Deleted] t 1 fIt 2 z (t ) dt . 8206 mean time to first failure (MTTFF) F: duree moyenne de fonctionnement avant la premiere defaillance (MTTFF) S: tiempo medio hasta el primer fallo (MTTFF) The expectation | f the time to first failure . 8207 mean time to failure (MTTF) F: duree moyenne de fonctionnement avant defaillance (MTTF) S: tiempo medio hasta el fallo (MTTF) The expectation | f the time to failure . 8208 mean time between failures (MTBF) F: moyenne des temps entre defaillances (MTBF) S: tiempo medio entre fallos (MTBF) The expectation | f the time between failures . 8209 failure rate acceleration factor F: facteur d'acceleration de la densite de defaillance; facteur d'acceleration du taux de defaillance S: factor de aceleracion de la tasa de fallos The ratio of the accelerated testing failure rate | o the failure rate under stated reference test conditions. Note - Both failure rates | efer to the same time period in the life of the tested items . 8210 failure intensity acceleration factor F: facteur d'acceleration de l'intensite de defaillance S: factor de aceleracion de la intensidad de fallos In a time interval | f given duration , whose beginning is specified by a fixed age of a repaired item , the ratio of the number of failures obtained under two different sets of stress con- ditions. 8.3 Maintainability performance 8301 maintainability F: maintenabilite S: mantenibilidad The probability | hat a given active maintenance action , for an item | nder given conditions of use can be carried out within a stated time interval , when the maintenance is performed under stated conditions and using stated procedures and resources. Note - In French the term maintenabilite | s also to denote the performance quantified by this probability . 8302 (instantaneous) repair rate, u(t) (symbol) F: densite (temporelle) (instantanee), de reparation, u (t) | symbole) S: tasa (instantanea) de reparaciones, u(t) | simbolo) The limit, if this exists, of the ratio of the conditional probability | hat the corrective maintenance action terminates in a time interval , (t , t +?63t ) to the length of this time inter- val , when ?63t tends to zero, given that the action had not ter- minated at the beginning of the time interval . Note - The instantaneous repair rate | s expressed by for- mula as: u (t ) = lim u (t ) = ?63 (t ) 0 63t ____________________________ where T | is the instant of time | f restoration . T | ay also represent the time to restoration . 8303 mean repair rate, u (tv1, | v2) (symbol) F: densite (temporelle) moyenne de reparation, u | fR (t1, | fIt2) (symbole) S: tasa media de reparaciones, u | fR (t1, | fIt2) (simbolo) The normalized integral of the instantaneous repair rate | ver a given time interval (t1, | fIt2). Note - The mean repair rate | s related to instantaneous repair rate as: u (t 1 , t 2) = [Formula Deleted] t 1 fIt 2 u (t ) dt . 8304 mean maintenance man-hours F: duree moyenne equivalente de maintenance S: duracion media equivalente de mantenimiento; media de horas-hombre de mantenimiento The expectation | f the maintenance man-hours . 8305 mean down time (MDT) F: temps moyen d'indisponibilite; duree moyenne d'indisponibilite (TMI) S: tiempo medio de indisponibilidad (TMI) The expectation | f the down time . 8306 mean repair time (MRT) F: duree moyenne de reparation S: tiempo medio de reparacion The expectation | f the repair time . 8307 p-fractile repair time F: quantile-p de la duree de reparation S: cuantil-p del tiempo de reparacion The p-fractile | alue of the repair time . 8308 mean active repair time (MART) F: duree moyenne de reparation active S: tiempo medio de reparacion activa The expectation | f the active repair time . 8309 p-fractile active repair time F: quantile-p de la duree de reparation active S: cuantil-p del tiempo de reparacion activa The p-fractile | alue of the active repair time . 8310 mean time to restoration (MTTR); mean time to recovery; mean time to repair (deprecated) F: duree moyenne de panne; moyenne des temps pour la t | che de reparation (MTTR) S: tiempo medio hasta el restablecimiento (MTTR) The expectation | f the time to restoration . 8311 fault coverage F: couverture de pannes S: cobertura de averias The proportion of faults | f an item | hat can be recognized under given conditions. 8312 repair coverage F: couverture des reparations S: cobertura de reparaciones The proportion of faults | f an item | hat can be success- fully removed. 8.4 Maintenance support performance 8401 mean administrative delay (MAD) F: duree moyenne du delai administratif S: retardo medio administrativo; demora media adminis- trativa The expectation | f the administrative delay . 8402 p-fractile administrative delay F: quantile-p du delai administratif S: cuantil-p del retardo administrativo; cuantil-p de la demora administrativa The p-fractile | alue of the administrative delay . 8403 mean logistic delay (MLD) F: duree moyenne du delai logistique S: retardo medio logistico; demora media logistica The expectation | f the logistic delay . 8404 p-fractile logistic delay F: quantile-p du delai logistique S: cuantil-p del retardo logistico; cuantil-p de la demora logistica The p-fractile | alue of the logistic delay . 9 Test, data, design and analysis 9.1 Test concepts 9101 test F: essai S: prueba An experiment made in order to measure or classify a charac- teristic . 9102 compliance test F: essai de conformite S: prueba de conformidad A test | sed to show whether or not a characteristic | f an item | omplies with the stated requirements. 9103 determination test F: essai de determination S: prueba de determinacion A test | sed to establish the value of a characteristic . 9104 laboratory test F: essai en laboratoire S: prueba de laboratorio A compliance test | r a determination test | ade under prescribed and controlled conditions which may or may not simulate field conditions. 9105 field test F: essai dans des conditions d'exploitation S: prueba en condiciones de explotacion; prueba en condiciones reales A compliance test | r determination test | ade in the field where operating, environmental, maintenance and measurement condi- tions are recorded. 9106 endurance test F: essai d'endurance S: prueba de resistencia A test | arried out over a time interval | o investigate how the properties of an item are affected by the application of stated stresses and by their time duration . 9107 accelerated test F: essai accelere S: prueba acelerada A test | n which the applied stress level is chosen to exceed that stated in the reference conditions in order to shorten the time duration required to observe the stress response of the item , or to magnify the responses in a given time duration . Note - To be valid, an accelerated test | hall not alter the basic fault modes and failure mechanisms , or their relative pre- valence. 9108 step stress test F: essai sous contrainte echelonnee S: prueba de esfuerzo escalonado A test | onsisting of several stress levels applied sequen- tially for periods of equal time duration | o an item , in such a way that during each time interval a stated stress level is applied and the stress level is increased from one time interval to the next. 9109 screening test F: essai de selection S: prueba de seleccion A test , or combination of tests , intended to remove or detect unsatisfactory items | r those likely to exhibit early failures . 9110 time acceleration factor F: facteur d'acceleration temporelle S: factor de aceleracion temporal The ratio between the time durations | ecessary to obtain the same stated number of failures | r degradations in two equal size samples under two different sets of stress conditions involving the same failure mechanisms and fault modes and their relative pre- valence. Note - One of the two sets of stress conditions should be a reference set. 9111 maintainability verification F: verification de la maintenabilite S: verificacion de la mantenibilidad A procedure applied for the purpose of determining whether the requirements for maintainability performance measures for an item has been achieved or not. Note - The procedures may range from analysis of appropriate data to a maintainability demonstration . 9112 maintainability demonstration F: verification experimentale de maintenabilite S: demostracion de la mantenibilidad A maintainability verification | erformed as a compliance test . 9.2 Data concepts 9201 observed data F: valeur observee; donnee observee S: datos observados; valores observados Values related to an item | r a process obtained by direct observation. Note - Values referred to could be events, time instants, time intervals , etc. 9202 test data F: donnees d'essai S: datos de prueba Observed data | btained during tests . 9203 field data F: donnee d'exploitation S: datos de explotacion Observed data | btained during field operation. 9204 reference data F: valeur de reference; donnees de reference S: datos de referencia; valores de referencia Data, which by general agreement may be used for prediction | nd/or comparison with observed data . 9.3 Design concepts 9301 redundancy F: redondance S: redundancia In an item , the existence of more than one means for perform- ing a required function . 9302 active redundancy F: redondance active S: redundancia activa That redundancy | herein all means for performing a required function | re intended to operate simultaneously. 9303 standby redundancy F: redondance en attente; redondance passive; redondance en secours S: redundancia pasiva; redundancia de reserva That redundancy | herein one means for performing a required function | s intended to operate, while the alternative means are inoperative until needed. 9304 fail safe F: protege contre defaillances (critique); a s | rete integree S: prevencion de fallos A designed property of an item | hich prevents its failures | rom resulting in critical faults . 9305 fault tolerance F: tolerance aux pannes S: tolerancia a las averias The attribute of an item | hat makes it able to perform a required function | n the presence of certain given sub-item faults . 9306 fault masking F: masquage de panne S: enmascaramiento de averia The condition in which a fault | xists in a sub-item of an item | ut cannot be recognized because of a feature of the item or because of another fault of the sub-item or of another sub-item. 9.4 Analysis concepts 9401 prediction F: prevision; prediction S: prevision; prediccion 1) The process of computation used to obtain (a) predicted | alue(s) of a quantity. 2) The predicted | alue(s) of a quantity. 9402 reliability model F: modele de fiabilite S: modelo de fiabilidad A mathematical model used for prediction | r estimation | f reliability measures | f an item or for similar purposes. 9403 fault modes and effects analysis (FMEA) F: analyse des modes de panne et de leurs effets (AMDE) S: analisis de los modos de averia y de sus efectos (AMAE) A qualitative method of reliability | nalysis which involves the study of the fault modes | hich can exist in every sub-item of the item and the determination of the effects of each fault mode on other sub-items of the item and on the required functions of the item . 9404 fault modes, effects and criticality analysis (FMECA) F: analyse des modes de panne, de leurs effets et de leur criticite (AMDEC) S: analisis de los modos de averia, sus efectos y su cri- ticidad (AMAEC) Fault modes and effect analysis | ogether with a considera- tion of the probability | f occurrence and a ranking of the seri- ousness of the fault . 9405 fault tree analysis (FTA) F: analyse par arbre de panne S: analisis en arbol de averias An analysis to determine which fault modes | f the sub-items or external events, or combinations thereof, may result in a stated fault mode of the item , resulting in a fault tree . 9406 stress analysis F: analyse de contraintes S: analisis de esfuerzos A quantitative or qualitative determination of the physical, chemical or other stresses an item | s subjected to under given use conditions. 9407 reliability block diagram F: diagramme de fiabilite S: diagrama de bloques de fiabilidad Block diagram showing, for one or more functional modes | f a complex item , how faults | f the sub-items represented by the blocks, or combinations thereof, result in a fault of the item . 9408 fault tree F: arbre de panne S: arbol de averias A logic diagram showing which fault modes | f sub-items or external events, or combinations thereof, result in a given fault mode of the item . 9409 state-transition diagram F: diagramme de transition S: diagrama de transicion de estados A diagram showing the set of possible states of an item | nd the possible one step transitions between these states. 9410 stress model F: modele de contraintes S: modelo de esfuerzos A mathematical model which describes how a reliability perfor- mance measure | f an item | aries as a function of the applied stresses. 9411 fault analysis F: analyse des pannes S: analisis de averias The logical, systematic examination of an item | r its diagram(s) to identify and analyse the probability , causes and consequences of potential and real faults . 9412 maintainability model F: modele de maintenabilite S: modelo de mantenibilidad A mathematical model used for prediction | r estimation | f maintainability performance measures of an item or for similar pur- poses. Note - An example is the maintenance tree . 9413 maintainability prediction F: prevision de maintenabilite; prediction de maintenabilite S: prevision de la mantenibilidad; prediccion de la mantenibilidad An activity performed with the intention to forecast the numerical values of a maintainability performance measure of an item , taking into account the maintainability performance and reliability performance measures of its sub-items, under given operational and maintenance conditions. 9414 maintenance tree F: arbre de maintenance S: arbol de mantenimiento A logic diagram showing the pertinent alternative sequences of elementary maintenance activities | o be performed on an item and the conditions for their choice. 9415 maintainability allocation; maintainability apportion- ment F: repartition de la maintenabilite S: distribucion de la mantenibilidad; asignacion de la mantenibilidad A procedure applied during the design of an item | ntended to apportion the requirements for maintainability performance measures for an item to its sub-items according to given criteria. 9.5 Improvement processes 9501 learning process F: apprentissage S: aprendizaje Growth in experience and familiarity by personnel with design or constructional techniques, which reduces the risk of future mis- takes . 9502 burn-in F: rodage S: rodaje A process of reliability improvement | f hardware, employing operation of every item | n a prescribed environment, with succes- sive fault correction , replacement or removal at every failure , during the steeply falling failure intensity period within the early failure period . 9503 reliability growth F: croissance de la fiabilite S: crecimiento de la fiabilidad; incremento de la fia- bilidad A condition characterized by a progressive improvement of a reliability performance measure | f an item , or population of similar items , with time. Note - A growth can result either from active improvement or from burn-in . 9504 reliability improvement F: amelioration de fiabilite S: mejora de la fiabilidad A process undertaken with the deliberate intention of promot- ing reliability growth | y the elimination of systematic faults . 9505 maintainability programme F: programme de maintenabilite S: programa de mantenibilidad A detailed plan, including the human and material resources, procedures, tasks and responsibilities during the life of an item , intended to determine the fulfilment of the requirements for main- tainability performance measures for an item and facilitate the planning of the maintenance . 10 Measure modifiers 1001 true | .. F: ... | rai S: ... | erdadero The ideal value which characterizes a quantity perfectly defined under the conditions which exist at the moment when that quantity is observed, or the subject of a determination. Note - This value could be arrived at only if all causes of measurement error were eliminated. 1002 predicted | .. F: ... | redit; ... | revu S: ... | revisto; ... | redicho The numerical value assigned to a quantity, before the quan- tity is actually observable, computed on the basis of earlier observed or estimated values of the same quantity or of other quan- tities using a mathematical model. 1003 extrapolated | .. F: ... | xtrapole S: ... | xtrapolado The predicted | alue based on estimated | alues for one or a set of conditions, intended to apply to other conditions such as time, maintenance and environmental conditions. 1004 estimated | .. F: ... | stime S: ... | stimado The value obtained as the result of an estimation . Note - The result may be expressed either as a single numeri- cal value, a point estimate, or as a confidence interval . 1005 intrinsic | ..; inherent | .. F: ... | ntrinseque; ... | nherent S: ... | ntrinseco; ... | nherente Value of a measure | etermined when maintenance and opera- tional conditions are assumed to be ideal. 1006 operational | .. F: ... | perationnel S: ... | peracional Value determined under given operational conditions. 1007 mean | ..; average | .. (deprecated) F: ... | oyen (adjectif) S: ... | edio (adjetivo); promedio | desaconsejado) 1) The value obtained as the expectation | f a random variable . 2) The normalized integral of a time dependant quantity. 1008 p-fractile | .. F: ... | uantile-p S: cuantil-p de | .. The value obtained as the p-fractile | f the distribution of a random variable . 1009 instantaneous | .. F: ... | nstantane S: ... | nstantaneo The value of a measure | etermined for a given instant of time . PART II Statistical vocabulary 1 Introduction The quantitative applications of measures for quality of ser- vice, network performance, dependability and trafficability perfor- mance requires a fundamental set of statistical concepts. This Part provides the terms and definitions for such applica- tions. 2 Terms and definitions 2001 characteristic F: caractere (statistique) S: caracteristica A property which helps to differentiate between the individu- als of a given population. Note - The differentiation may be either quantitative (by variables) or qualitative (by attributes). 2002 probability F: probabilite S: probabilidad For practical reasons, it may be considered that, whenever the conditions of a test | an be reproduced, the probability Pr (E) | of an event E | ccurring is the value around which the occurrence frequency of the latter oscillates and towards which it tends when the number of tests are indefinitely increased. Note - The concept of probability | ay be introduced in either of two forms, depending on whether it is intended to desig- nate a degree of belief or whether it is considered as the limit value of a frequency. In both cases, its introduction requires that some precautions be taken which cannot be developed within the con- text of an International Standard and for which users should refer to specialized literature. 2003 random variable; variate F: variable aleatoire S: variable aleatoria A variable which may take any of the values of a specified set of values and with which is associated a probability distribution. Note - A random variable | hich may take only isolated values is said to be "discrete". A random variable | hich may take all the values of a finite or infinite interval is said to be "con- tinuous". 2004 random process F: processus aleatoire; processus stochastique S: proceso aleatorio; proceso estocastico A collection of time-dependent random variables | here the values are governed by a given set of multivariate distributions for all combinations of the random variables . 2005 distribution function F: fonction de repartition S: funcion de distribucion A function giving, for every value x , the probability | hat the random variable X | s less than or equal to x : F (x ) = Pr (X x ). 2006 probability density function F: densite de probabilite S: funcion densidad de probabilidad The derivative, if this exists, of the distribution function : f (x ) = X ____ . 2007 p-fractile; p-quantile (of a probability distribution) F: quantile d'ordre p; quantile-p (d'une loi de probabilite) S: cuantil-p; cuantil de orden p (de una ley de distribucion de probabilidades) If p | s a number between 0 and 1, the p-fractile | s the value of the random variable | or which the distribution function equals p or "jumps" from a value less than or equal to p to a value greater than p . Note - It is possible that the distribution function | quals p throughout the interval between consecutive possible values of the variate. In this case, any value in this interval may be considered as the p-fractile . 2008 expectation (of a random variable); mean (of a random variable) F: esperance mathematique (d'une variable aleatoire); moyenne (d'une variable aleatoire) S: esperanza matematica (de una variable aleatoria); media (de una variable aleatoria) a) For a discrete random variable X | aking the values xiwith the probabilites pi, E (X ) = ~" p i x i the sum being extended over all the values xiwhich can be taken by X . b) For a continuous random variable X | aving the probability density function f (x ), E (X ) = x f (x ) dx the integral being extended over all values of the interval of variation of X . Note 1 - No distinction is made between the expectation | f a random variable | nd that of a probability distribution. Note 2 - The term mean | s also used with other meanings, for example as the normalized integral over a time interval . 2009 variance (of a random variable) F: variance (d'une variable aleatoire) S: varianza (de una variable aleatoria) The expectation | f the square of the difference between a random variable | nd the expectation of this variable. 2010 standard deviation, ` (symbol) F: ecart-type, ` (symbole) S: desviacion tipica, ` (simbolo) The positive square root of the variance . 2011 observed value (in statistics) F: valeur observee (en statistique) S: valor observado (en estadistica) The value of a characteristic | etermined as the result of an observation or test . 2012 relative frequency F: frequence (statistique) S: frecuencia relativa The ratio of the number of times a particular value, or a value falling within a given class, is observed to the total number of observations. 2013 statistical test F: test (statistique) S: prueba estadistica A procedure that is intended to decide whether a hypothesis about the distribution of one or more populations should be rejected or not rejected (accepted). Note 1 - The decision taken is a result of the value of an appropriate statistic | r statistics , calculated from values observed in samples taken from the populations under consideration. As the value of the statistic is subject to random variations, there is some risk of error when the decision is taken. Note 2 - It is important to note that, generally speaking, a test | ssumes a priori | hat certain assumptions are fulfilled (for example, assumption of independence of the observations, assumption of normality, etc.). These assumptions serve as a basis of the test . 2014 one-sided test F: test unilateral S: prueba unilateral A statistical test | n which the statistic | sed is one-dimensional and the critical region is the set of values lower than, or the set of values greater than, a given number. 2015 two-sided test F: test bilateral S: prueba bilateral A statistical test | n which the statistic | sed is one-dimensional and in which the critical region is the set of values lower than a first given number and the set of values greater than a second given number. 2016 null hypothesis, Hv0 (symbol) F: hypothese nulle, H0(symbole) S: hipotesis nula, H0(simbolo) The hypothesis to be rejected or not rejected (accepted) at the outcome of the statistical test . 2017 alternative hypothesis, Hv1 (symbol) F: hypothese alternative, H1 | symbole) S: hipotesis alternativa, H1 | simbolo) The hypothesis, usually composite, which is opposed to the null hypothesis 2018 critical region F: region critique S: region critica The set of possible values of the statistic | sed such that, if the value of the statistic | hich results from the observed values belongs to the set, the null hypothesis will be rejected, whereas it will not be rejected (accepted) if the opposite is the case. 2019 critical values F: valeurs critiques S: valores criticos The given value(s) which limit the critical region . 2020 error of the first kind F: erreur de premiere espece S: error de primera clase The error | ommitted in rejecting the null hypothesis , because the statistic | akes a value which belongs to the critical region , when the null hypothesis is true. 2021 type I risk F: risque de premiere espece S: riesgo de tipo I The probability | f committing the error of the first kind , which varies according to the real situation (within the framework of the null hypothesis ). Its maximum value is the significance level of the statistical test . 2022 error of the second kind F: erreur de seconde espece S: error de segunda clase The error | ommitted in failing to reject (accept) the null hypothesis | because the value of the statistic does not belong to the critical region ), when the null hypothesis is not true (the alternative hypothesis therefore being true). 2023 type II risk F: risque de seconde espece S: riesgo de tipo II The probability , designated |, of committing the error of the second kind . Its value depends on the real situation and can only be calculated if the alternative hypothesis is adequately speci- fied. 2024 operating characteristic curve; OC curve (for a sta- tistical test plan) F: courbe d'efficacite (d'un plan de test) S: curva caracteristica de funcionamiento (para un plan de prueba estadistica) A curve showing, for a given statistical test | lan, the pro- bability of acceptance | s a function of the actual value of a given measure . 2025 producer's risk (point) F: (point du) risque du fournisseur S: (punto de) riesgo del proveedor A point on the operating characteristic curve | orresponding to some predetermined and usually low probability of rejection . 2026 consumer's risk (point) F: (point du) risque du client S: (punto de) riesgo del consumidor A point on the operating characteristic curve | orresponding to a predetermined and usually low probability of acceptance . 2027 power of the test F: puissance du test S: potencia de la prueba The probability | f not committing the error of the second kind , equal to 1 | (em | (*a, and thus the probability of reject- ing the null hypothesis when this hypothesis is false. 2028 significance level (of a statistical test), ( (symbol) F: niveau de signification (d'un test); seuil de sig- nification, ( | (symbole) S: nivel de significacion (de una prueba estadistica); umbral de significacion, ( | (simbolo) The given value which limits the probability | f the null hypothesis | eing rejected, if the null hypothesis is true. Note - The critical region | s determined in such a way that if the null hypothesis | s true, the probability of this null hypothesis being rejected should be not more than this given value. 2029 probability of acceptance F: probabilite d'acceptation S: probabilidad de aceptacion The probability | hat an item | ill be accepted by a given statistical test | lan. 2030 probability of rejection F: probabilite de rejet S: probabilidad de rechazo The probability | hat an item | ill not be accepted by a given statistical test | lan. 2031 confidence interval F: intervalle de confiance S: intervalo de confianza The random interval limited by two statistics | r by a single statistic , such that the probability that a parameter to be estimated is covered by this interval is equal to a given value 1 | (em | (*a, where ( is the significance level . 2032 statistical tolerance interval F: intervalle statistique de dispersion S: intervalo estadistico de tolerancia A random interval limited by two statistics | r by a single statistic , such that the probability that a fraction of the popu- lation, equal to or greater than a given value between 0 and 1, is covered by this interval is equal to a given value 1 | (em | (*a, where ( is the significance level . 2033 confidence limit F: limite de confiance S: limite de confianza Each of the limits of a two-sided confidence interval , or the single limit of a one-sided confidence interval . 2034 estimation F: estimation (de parametres) S: estimacion (de parametros) The operation made for the purpose of assigning, from the observed values in a sample, numerical values to the parameters of the distribution chosen as the statistical model of the population from which this sample is taken. 2035 estimate F: estimation S: estimacion The result of an estimation . Note - This result may be expressed either as a single numer- ical value (point estimation) or as a confidence interval . 2036 estimator F: estimateur S: estimador A statistic | ntended to estimate a population parameter. 2037 confidence coefficient; confidence level F: niveau de confiance S: coeficiente de confianza; nivel de confianza The value 1 | (em | (*a of the probability | ssociated with a confidence interval | r a statistical tolerance interval , where ( is the significance level . 2038 statistic F: statistique S: estadistico A function of the observed values | erived from a sample. 2039 acceptable level (of a measure) F: niveau acceptable (d'une caracteristique) S: nivel aceptable (de una medida) A level for a measure | f a given performance which in a test | lan corresponds to a specified but relatively high probability of acceptance . ANNEX A (to Supplement 6) Alphabetical list of definitions contained in this Supplement 2 col 9107 accelerated test 2039 acceptable level 7209 accumulated down time 3010 accumulated time 7107 active corrective maintenance time 7103 active maintenance time 7106 active preventive maintenance time 9302 active redundancy 7107 active repair time 7109 administrative delay 5209 ageing failure 5311 ageing fault 2017 alternative hypothesis 8105 asymptotic availability 8106 asymptotic unavailability 8107 asymptotic mean availability 8108 asymptotic mean unavailability 6012 automatic maintenance 8105 availability 4002 availability performance 1007 average (deprecated) 5102 bug 9502 burn in 5509 busy state 5212 cataleptic failure 5212 catastrophic failure (deprecated) 2001 characteristic 7113 check-out time 9102 compliance test 5314 complete fault 2037 confidence coefficient 2031 confidence interval 2037 confidence level 2033 confidence limit 7307 constant failure intensity period 7308 constant failure rate period 2026 consumer's risk (point) 6023 controlled maintenance 6005 corrective maintenance 7105 corrective maintenance time 5103 critical defect 5108 critical defective item 5202 critical failure 5302 critical fault 2018 critical region 5510 critical state 2019 critical value 5313 data sensitive fault 5101 defect 5107 defective 5107 defective item 6006 deferred maintenance 5211 degradation failure 4001 dependability 5111 design defect 5207 design failure 5309 design fault 5318 determinate fault 9103 determination test 5219 deterministic failure 5505 disabled state 7207 disabled time 2005 distribution function 5507 down state 7208 down time 5211 drift failure 4006 durability 3009 duration 7306 early failure period 6020 elementary maintenance activity 9106 endurance test 3001 entity 5401 error 5505 error (deprecated sense) 2020 error of the first kind 2022 error of the second kind 2035 estimate 1004 estimated . | | 2034 estimation 2036 estimator 5402 execution error 2008 expectation 5506 external disabled state 7210 external disabled time 7210 external loss time 1003 extrapolated . | | 9304 fail safe 5201 failure 5217 failure cause 8204 failure intensity 8210 failure intensity acceleration factor 5218 failure mechanism 5322 failure mode (deprecated) 8202 failure rate 8209 failure rate acceleration factor 5301 fault 9411 fault analysis 6027 fault correction 7111 fault correction time 8311 fault coverage 6025 fault diagnosis 6026 fault localization 7114 fault localization time 6024 fault location (deprecated) 7114 fault location time (deprecated) 9306 fault masking 5322 fault mode 9404 fault modes, effects and criticality analysis (FMECA) 9403 fault modes and effects analysis (FMEA) 6024 fault recognition 9305 fault tolerance 9408 fault tree 9405 fault tree analysis (FTA) 5323 faulty 9203 field data 6009 field maintenance 9105 field test 9403 FMEA (fault modes and effects analysis) 9404 FMECA (fault modes, effects and criticality analysis) 5504 free state 7206 free time 9405 FTA (fault tree analysis) 6013 function affecting maintenance 6028 function check-out 6015 function-degrading maintenance 6016 function permitting maintenance 5314 function preventing fault 6014 function-preventing maintenance 3006 functional mode 5402 generated error 5211 gradual failure 5504 idle state 7206 idle time 5106 imperfection 6019 indenture level 5319 indeterminate fault 5206 inherent weakness failure 1005 inherent . | | 5308 inherent weakness fault 6009 in situ maintenance 3007 instant of time 1009 instantaneous . | | 8101 instantaneous availability 8111 instantaneous availability of a leased circuit 8204 instantaneous failure intensity 8202 instantaneous failure rate 8302 instantaneous repair rate 8102 instantaneous unavailability 5403 interaction error 5317 intermittent fault 5507 internal disabled state 1005 intrinsic . | | 3001 item 9104 laboratory test 5320 latent fault 9501 learning process 6017 level of maintenance 6018 line of maintenance 7110 logistic delay 8301 maintainability 9415 maintainability allocation 9415 maintainability apportionment 9112 maintainability demonstration 9412 maintainability model 4004 maintainability performance 9413 maintainability prediction 9506 maintainability programme 9111 maintainability verification 6003 maintenance 6021 maintenance action 6018 maintenance echelon 6030 maintenance entity 7102 maintenance man-hours (MMH) 6001 maintenance philosophy 6002 maintenance policy 4005 maintenance support performance 6021 maintenance task 7101 maintenance time 9414 maintenance tree 5105 major defect 5109 major defective item 5304 major fault 5112 manufacturing defect 5208 manufacturing failure 5310 manufacturing fault 8110 MADT (mean accumulated down time) 8308 MART (mean active repair time) 8401 MAD (mean administrative delay) 8305 MDT (mean down time) 2008 mean 1007 mean . | | 8110 mean accumulated down time (MADT) 8308 mean active repair time (MART) 8401 mean administrative delay (MAD) 8103 mean availability 8305 mean down time (MDT) 8203 mean failure rate 8205 mean failure intensity 8403 mean logistic delay (MLD) 8304 mean maintenance man-hours 8303 mean repair rate 8306 mean repair time (MRT) 8208 mean time between failures (MTBF) 8207 mean time to failure (MTTF) 8206 mean time to first failure (MTTFF) 8310 mean time to recovery 8310 mean time to repair (deprecated) 8310 mean time to restoration (MTTR) 8104 mean unavailability 8109 mean up time (MUT) 3011 measure 5106 minor defect 5110 minor defective item 5305 minor fault 5205 mishandling failure 5307 mishandling fault 5405 mistake 5204 misuse failure 5306 misuse fault 8403 MLD (mean logistic delay) 7102 MMH (maintenance man-hours) 8306 MRT (mean repair time) 8208 MTBF (mean time between failures) 8207 MTTF (mean time to failure) 8206 MTTFF (mean time to first failure) 8310 MTTR 8109 MUT (mean up time) 3013 modification 5104 non-critical defect 5203 non-critical failure 5303 non-critical fault 5214 non-relevant failure 3003 non-repaired item 5502 non-operating state 7202 non-operating time 7204 non-required time 2016 null hypothesis 9201 observed data 2011 observed value 2024 OC curve 6010 off-site maintenance 2014 one-sided test 6009 on-site maintenance 2024 operating characteristic curve 5501 operating state 7201 operating time 3012 operation 1006 operational . | | 5505 outage 5315 partial fault 5316 permanent fault 5316 persistent fault 2007 p-fractile (of a probability distribution) 1008 p-fractile . | | 8309 p-fractile active repair time 8402 p-fractile administrative delay 8404 p-fractile logistic delay 8307 p-fractile repair time 8101 pointwise availability 8102 pointwise unavailability 2027 power of the test 1002 predicted . | | 9401 prediction 6004 preventive maintenance 7104 preventive maintenance time 5215 primary failure 2002 probability 2006 probability density function 2029 probability of acceptance 2030 probability of rejection 2025 producer's risk (point) 5312 programme-sensitive fault 5404 propagated error 2007 p-quantile 2004 random process 2003 random variable 6029 recovery 9301 redundancy 9204 reference data 8201 reliability 9407 reliability block diagram 9503 reliability growth 9504 reliability improvement 9402 reliability model 4003 reliability performance 2012 relative frequency 5213 relevant failure 6011 remote maintenance 6005 repair 8312 repair coverage 8302 repair rate 7105 repair time 3002 repaired item 5219 reproducible failure 3005 required function 7203 required time 6029 restoration 6007 scheduled maintenance 5216 secondary failure 9109 screening test 2028 significance level 5316 solid fault 2010 standard deviation 9303 standby redundancy 5503 standby state 7205 standby time 9409 state-transition diagram 2038 statistic 2013 statistical test 2032 statistical tolerance interval 8105 steady-state availability 9108 step stress test 9406 stress analysis 9410 stress model 5210 sudden failure 6001 supervision 5219 systematic failure Blanc 5321 systematic fault 7112 technical delay 9101 test 9202 test data 9110 time acceleration factor 7303 time between failures 3009 time duration 7302 time to failure 7301 time to first failure 3008 time interval 7304 time to recovery 7304 time to restoration 5317 transient fault 1001 true . | | 2015 two-sided test 2021 type I risk 2023 type II risk 7108 undetected fault time 5508 up state 7211 up time 6008 unscheduled maintenance 7305 useful life 2009 variance 9203 variate 5317 volatile fault 5206 weakness failure 5308 weakness fault 5209 wearout failure 5311 wearout fault 7309 wear-out failure period Blanc ANNEX B (to Supplement 6, Part I) Relations between defect, failure and fault concepts H.T. [T1.6] TABLE B-1 ______________________________________________________________________________ Defect Failure Fault ______________________________________________________________________________ Critical defect Critical failure Critical fault Non-critical defect Non-critical failure Non-critical fault Major defect - Major fault Minor defect - Minor fault - Misuse failure Misuse fault - Mishandling failure Mishandling fault - Inherent weakness failure Inherent weakness fault Design defect Design failure Design fault Manufacturing defect Manufacturing failure Manufacturing fault - Ageing failure Ageing fault - Sudden failure - - Gradual failure - - Cataleptic failure - - Relevant failure - - Non-relevant failure - - Primary failure - - Secondary failure - - Failure cause - - Failure mechanism - - - Programme-sensitive fault - - Data-sensitive fault - - Complete fault - - Partial fault - - Persistent fault - - Intermittent fault - - Fault mode - - Determinate fault - - Indeterminate fault - - Latent fault - Systematic failure Systematic fault Bug - - ______________________________________________________________________________ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Table B-1/Sup. 6 [T1.6], p. Blanc ANNEX C (to Supplement 6, Part I) List of recommended symbols and abbreviations ( Significance level | Type II risk \(t ) Instantaneous failure rate \ (t1, | fIt2) Mean failure rate [in time interval (t1, | fIt2)] u(t ) Instantaneous repair rate u | (t1, | fIt2) Mean repair rate [in time interval (t1, | fIt2)] ` Standard deviation A Asymptotic availability A (t ) Instantaneous availability A | Asymptotic mean availability A | (t1, | fIt2) Mean availability [in time interval (t1, | fIt2)] ASR Answer seizure ratio E (X ) Mean (of X ) f (x ) Probability density function F (x ) Distribution function FMEA Fault modes and effect analysis FMECA Fault modes, effects and criticality analysis FTA Fault tree analysis H0 Null hypothesis H1 Alternative hypothesis MAD Mean administrative delay MADT Mean accumulated down time MART Mean active repair time MDT Mean down time MLD Mean logistic delay MMH Maintenance man-hours MRT Mean repair time MTBF Mean time between failures MTTF Mean time to failure MTTFF Mean time to first failure MTTR Mean time to restoration MUT Mean up time N (t1, t2) Number of failures [in time interval (t1, | fIt2)] R Reliability U Asymptotic unavailability U (t ) Instantaneous unavailability U | Asymptotic mean unavailability U | (t1, | fIt2) Mean unavailability [in time interval (t1, | fIt2)] z (t ) Instantaneous failure intensity z | (t1, | fIt2) Mean failure intensity [in time interval (t1, | fIt2)] Blanc Supplement No. 7 GUIDE FOR EVALUATING AND IMPLEMENTING | fR ALTERNATE ROUTING NETWORKS A systematic procedure consisting of a number of distinct steps is used for the evaluation of alternate routing networks. These steps are given in the flowchart of Annex A and are pro- vided as guidance. Administrations may wish to expand, delete or change the order of these steps to meet circumstances. The steps may be grouped into the following six processes: - Identification of alternate route. - Preliminary screening. - Data gathering. - Evaluation. - Implementation. - Monitoring. 1 Identification of alternate route A terminal Administration selects an alternate route. A tentative agreement is reached with the opposite terminal Administration to use the selected alternate route, and both termi- nal Administrations reach tentative agreement with the transit Administration to explore the use of its network as an alternate route. If no tentative agreements are reached, another alternate route is selected or if none is available, the procedure is aban- doned. 2 Preliminary screening Using available data, the organizational elements of the ter- minal Administrations responsible for transmission, routing and call completion, analyse the feasibility of utilizing the alternate route. If an objection is raised, another alternate route is selected or, if none is available, the procedure is abandoned. 3 Data gathering A questionnaire is issued to all Administrations involved to obtain additional information before an evaluation is made of the proposed alternate route. The questionnaire can include requests for transmission, rout- ing, call completion rates, traffic profiles, circuit costs, and transit charges. If there is no response to the questionnaire or if the infor- mation provided indicates that the alternate route is unsuitable, another alternate route is selected or, if none is available, the procedure is abandoned. 4 Evaluation The alternate routing network is dimensioned according to Recommendation E.522. If additional circuits are required on the alternate route, and the required increment exceeds the available capacity, another alternate route is selected. If no other alternate route is available Administrations may choose to retain the selected alter- nate route and accept a cost disadvantage. 5 Implementation Final negotiations are carried out and approval of all Administrations involved in the alternate route network is sought. The negotiations would include the reporting procedure and responsibility for recording traffic overflowing to the alternate route. If final agreement cannot be reached, another alternate route is selected or, if none is available, the procedure is abandoned. 6 Monitoring Traffic volumes and performance data for the alternate route are recorded and exchanged at regular intervals. ANNEX A (to Supplement No. 7) Flowchart of evaluation and implementation procedure for alternate routing networks Figure A-1, p. Blanc Figure A-2, p.