5i' SECTION 8 TRANSMISSION QUALITY ABOVE 50 BAUDS Recommendation R.120 TOLERABLE LIMITS FOR THE DEGREE OF ISOCHRONOUS DISTORTION OF CODE-INDEPENDENT TELEGRAPH CIRCUITS OPERATING AT MODULATION RATES OF 75, 100 AND 200 BAUDS (Geneva, 1976; amended at Geneva, 1980) The CCITT, considering (a) that, to facilitate the study of plans for the establish- ment of international telegraph circuits, it is convenient to set limits for the degree of isochronous distortion of telegraph cir- cuits and channels; (b) that, for whatever purposes normally used, these circuits should be capable of use with start-stop equipment; (c) that, until detailed transmission planning standards are established for the trunk sections of international telegraph cir- cuits operating at modulation rates of 75, 100 and 200 bauds, the distortion limits mentioned below should be regarded as provisional standards; (d) that the limits laid down are those that should be evident in service conditions on telegraph circuits, excluding the local lines and terminal equipment, unanimously declares the view (1) that circuits (excluding local lines and terminal equip- ment) should be established and maintained in such a manner that the degree of isochronous distortion will not exceed the limits shown in Table 1/R.120, irrespective of whether any form of regeneration is provided in the circuit or not; H.T. [T1.120] TABLE 1/R.120 _____________________________________________________ Modulation rate (bauds) { Maximun degree of isochronous distortion permitted } _____________________________________________________ 75 28 | 100 24 | 200 32 | _____________________________________________________ | | | | | | | | | | | | | | | | | | | | | | | | | | | TABLE 1/R.120 (R.) [T1.120] p.182 (2) that the degree of isochronous distortion of each channel that may form part of a circuit should be as small as possible, and should not in any case exceed 10%. Recommendation R.121 STANDARD LIMITS OF TRANSMISSION QUALITY FOR START-STOP USER CLASSES OF SERVICE 1 AND 2 ON ANISOCHRONOUS DATA NETWORKS (Geneva, 1976) The CCITT, considering (a) that, to permit the sharing of responsibility for the maintenance of a high standard of transmission quality on switched connections between anisochronous data networks referred to in Recommendation X.1 [1], it is necessary to specify limiting values of distortion on signals leaving the international gateway centre of each network; (b) that, on the other hand, to enable national switched net- works to be interconnected, it is necessary to have a distribution plan of the telegraph distortion between national networks and the international junction circuits connecting the international gate- way switching centres; (c) that it is difficult to lay down standards applicable both to small and to large national networks; (d) that it should be possible to fix limit values for large countries and they should apply to the great majority of user loca- tions taking part in the international service, unanimously declares the view 1 The following standards of transmission quality should be observed for the interconnection of national anisochronous data networks set up by means of transmission channels and start-stop terminal equipment in accordance with CCITT Recommendations to pro- vide service for user classes of service 1 and 2 to Recommendation X.1 [1] (up to and including 300 bit/s). 1.1 The degree of gross start-stop distortion in service (i.e. including the effect of distortion due to the sending termi- nal equipment and the switching centres) at the point of exit of the national network should provisionally not exceed 22%. Note - The international gateway exchange of a country is considered as forming part of the national network of that country. 1.2 The degree of inherent start-stop distortion of the inter- national junction circuit should provisionally not exceed 13%. Note 1 - In establishing the provisional 13% limit for the degree of start-stop distortion in the international junction cir- cuit account has been taken of the fact that in a global connec- tion, the international junction circuit might consist of 2 chan- nels in tandem. If the international junction circuit is esta- blished on a single channel, an 8% provisional limit would be applicable to that circuit. Note 2 - No limit for distortion on the entry to an interna- tional gateway centre at the receiving end has been indicated in this Recommendation. The values mentioned in SS 1.1 and 1.2 above are adequate for planning purposes. 2 The provisional limit values mentioned above are applicable to large countries that are directly interconnected without switch- ing in a transit country. Where national networks are unable to satisfy S 1.1 above, signal regeneration will be required. 3 Small countries (defined as countries in which all user ter- minal equipment can be reached via not more than one carrier chan- nel in the national network) will have to try to obtain values less than the maximum 22% distortion mentioned in S 1.1 above. 4 The provisional standard limits mentioned under S 1 above can also apply to private switched telegraph and anisochronous data networks. Reference [1] CCITT Recommendation International user classes of ser- vice in public data networks , Rec. X.1. Recommendation R.122 SUMMARY OF TRANSMISSION PLANS FOR RATES UP TO 300 BAUDS (Melbourne, 1988) The CCITT, considering (a) that this Recommendation summarizes the distortion limits to be used in formulating transmission plans for connections work- ing at rates up to 300 bauds; (b) that User Classes of Services 1 and 2 in Recommendation X.1 should be taken into account; (c) that the rates and codes given in Recommendation R.101 should be taken into account; (d) that Recommendations R.20, R.50, R.57, R.58, R.120, R.121 and S.3 should be taken into account, unanimously declares the view In planning international point-to-point and switched tele- graph communications, Administrations should use the following as a guide. The individual recommendations referred to should be taken into account. Note 1 - Most of the figures given were derived using the laws of addition of distortion appropriate to analogue transmission equipment MCVFT, however were another law is known to apply TDM, then the appropriate law of addition should be used (see Recommendation R.11). Note 2 - Most of the figures given relate to start-stop dis- tortion but some, R.20, R.120 and R.58 for trunk distortion, relate to isochronous distortion. As a first approximation, isochronous and start-stop distortion may be considered to be equivalent for small values. However the individual Recommendations should be taken into account in each case. In the following examples: T is the customers terminal, M is a modem to Recommendation R.20, | (ra represents the transmit distortion from the given point, | represents the margin at the given point, | (<- | represents the distortion introduced between the given points. Blanc Figure T0900310-89, p. 2 Figure T0900320-89, p. 3 Figure T0900330-89, p. 4 Figure T0900340-89, p. 5 Figure T0900350-89, p. 6 Figure T0900360-89, p. 7 Figure T0900370-89, p. 8 Figure T0900380-89, p. 9 MONTAGE: PAGE PAIRE = PAGE BLANCHE SECTION 9 DEFINITIONS Recommendation R.140 DEFINITIONS OF ESSENTIAL TECHNICAL TERMS IN THE FIELD OF TELEGRAPH TRANSMISSION (Geneva, 1980 amended at Malaga-Torremolinos, 1984 and Melbourne, 1988) Note - Each term is designated by a number in the original CCITT numbering scheme and additionally by the nearest equivalent number in Chapter 721 of the IEV. 02 SERIES - GENERAL TRANSMISSION PROCESSES 02.081 hypothetical reference connection (in telegraphy); hypothetical reference circuit (deprecated) F: communication fictive de reference (en telegraphie); circuit fictif de reference (terme deconseille) S: conexion ficticia de referencia (en telegrafia); circuito ficticio de referencia (desaconsejado) Hypothetical connection made up for two terminals in the world telex network, or other telegraph network, corresponding in princi- ple to the most onerous case in order to study the transmission and switching characteristics necessary to ensure satisfactory opera- tion. 721.33.14 02.24 subtelephone telegraphy F: telegraphie infra-telephonique S: telegrafia infratelefonica; telegrafia infraacustica Telegraphy using a frequency band below that part of the audio range usually employed in telephone transmission. 02.25 super-telephone telegraphy F: telegraphie supra-telephonique S: telegrafia supratelefonica; telegrafia supraacustica Telegraphy using a frequency band above that part of the audio range usually employed in telephone transmission. 31 SERIES - GENERAL ALPHABETIC TELEGRAPHY 31.01 code character F: caractere (telegraphique) S: caracter de codigo The set of conventional elements established by the code to enable the transmission of a written character (letter, figure, punctuation sign, arithmetical sign, etc.) or the control of a par- ticular function (spacing, shift, line-feed, carriage return, phase correction, etc.); this set of elements being characterized by the variety, the duration and the relative position of the component elements (or by some of these features). Note - The French and English terms are not equivalent. 31.011 telegraph signal F: signal telegraphique S: se~al telegrafica A signal representing all or part of one or more telegraph messages. 721.31.03 31.02 signal element F: element de signal S: elemento de se~al Each of the parts constituting a signal and distinguished from the others by one or more characteristics such as its nature, mag- nitude, duration and relative position. 721.21.06 31.021 transition F: transition S: transicion A transient phenomenon separating two successive signal ele- ments having different significant conditions. 721.21.28 31.022 change-over F: mutation S: cambio A change from one significant condition to another. 721.21.27 31.023 character signal F: signal de caractere S: se~al de caracter A set of signal elements representing a character. 721.22.10 31.024 character format F: format de caractere S: formato de caracter A general description of a character signal, indicating for example the number of unit elements it contains. 31.025 character length Number of unit intervals contained in a character signal. 31.05 start signal F: signal de depart S: se~al de arranque In start-stop transmission, a signal preceding each group of signal elements which prepares the receiving device for the recep- tion of the elements of the group. 721.22.15 31.051 start element F: element de depart S: elemento de arranque A start signal limited to one signal element generally having the duration of a unit interval. 721.22.16 31.06 stop signal F: signal d'arr | t S: se~al de parada In start-stop transmission, a signal following each group of signal elements which prepares the receiving device for the recep- tion of the subsequent start signal, or brings the device to rest. 721.22.17 31.061 stop element F: element d'arr | t S: elemento de parada A stop signal limited to one signal element having any dura- tion equal to or greater than a specified minimum value. 721.22.18 31.07 telegraph code F: code telegraphique S: codigo telegrafico A system of rules and conventions according to which a succes- sion of significant conditions representing a message should be formed and translated in alaphabetic telegraphy. 721.31.05 31.08 telegraph alphabet F: alphabet telegraphique S: alfabeto telegrafico A convention indicating correspondence between a set of char- acters and a set of groups of elements which represent them. 721.31.07 31.081 n-unit code alphabet F: alphabet d'un code a n moments S: alfabeto de codigo de n unidades A telegraph alphabet indicating correspondence between a set of characters and a set of n-unit code combinations. 721.31.08 31.082 international telegraph alphabet No. 1 (ITA1) F: alphabet telegraphique international n (ATI n S: alfabeto telegrafico internacional N. (ATI N. A telegraph alphabet using a two-condition five-unit code, used in Baudot synchronous telegraphy. Note - This alphabet is specified by Article 16 of the Tele- graph Regulations, Geneva 1958. 721.31.09 31.083 international telegraph alphabet No. 2 (ITA2) F: alphabet telegraphique international n (ATI n S: alfabeto telegrafico internacional N. (ATI N. An alphabet using a two-condition five-unit code, used in start-stop telegraphy generally for teleprinters. Note - This alphabet is specified in Recommendation S.1. 721.31.10 31.084 international telegraph alphabet No. 3 (ITA3) F: alphabet telegraphique international n (ATI n S: alfabeto telegrafico internacional N. (ATI N. An alphabet using the two-condition seven-unit constant-ratio code. Note - This alphabet is defined by CCIR Recommendation 342-2 or CCITT Recommendation S.13 (1972). 721.31.11 31.085 international telegraph alphabet No. 4 (ITA4) F: alphabet telegraphique international n (ATI n S: alfabeto telegrafico internacional N. (ATI N. An alphabet using a two-condition six-unit code for the time division multiplex synchronous telegraphy, comprising in particular two code combinations corresponding to the permanent conditions A and Z, so that the multiplex channel can be operated in a switched network. Note - This alphabet is defined in Recommendation R.44 (1968). 721.31.12 31.086 international alphabet No. 5 (IA5) F: alphabet international n S: alfabeto internacional N. An alphabet using a two-condition eight-unit code with seven primary information elements and one parity check element, compris- ing in particular upper and lower case characters, diacritical signs and miscellaneous control functions. Note - The character coding rules using the seven primary elements are the subject of Recommen dations T50 and V.4. 721.31.13 31.09 character F: caractere (d'ecriture) S: caracter A member of a set of elements agreed upon to be used for organisation, representation or control of information. Note - Characters may be letters, digits, punctuation marks or other symbols and, by extension, function controls such as space, shift, carriage return or line-feed contained in a message. 721.22.09 31.10 equal-length code F: code a moments S: codigo de igual longitud A code, the character signals of which are composed of the same number of unit elements. 721.22.21 31.11 n-unit code F: code a n moments; code a n elements (unitaires) S: codigo de n unidades; codigo de n elementos uni- tarios Equal-length code according to which the character signals are composed of n unit elements. 721.22.22 31.111 code combination F: combinaison de code S: combinacion de codigo A combination of n-unit elements formed in accordance with an n-unit code which assigns a significant condition to each of the unit elements. 721.22.23 31.112 code element F: element de code S: elemento de codigo A unit element constituting part of a character signal from the arrangements of which a code combination is formed. Note - Figure 1/R.140 shows an example of the use of this term. Figure 1/R.140, p. 31.113 redundant code F: code redondant S: codigo redundante A code using more signal elements than strictly necessary to represent the contents of the message. For example: 1. A seven-unit code, such as International Telegraph Alpha- bet No. 3 which uses only character signals made of four unit ele- ments of A condition and three unit elements of Z condition, is redundant. 2. A five-unit code, using all the characters of Interna- tional Telegraph Alphabet No. 2, is not redundant. 721.27.23 31.12 code conversion F: conversion de code S: conversion de codigo The conversion from a representation of coded information to another representation of the same information in accordance with another code. Example: Conversion of character signals or groups of charac- ter signals in one telegraph code into corresponding signals or groups of signals in another code. 721.21.21 31.14 semateme (not used in English) F: semateme (a l'emission) S: sematema Contiguous succession in time of significant conditions. 721.31.14 31.15 restitution F: restitution S: restitucion The formation of a succession in time of signifcant conditions resulting from a received signal. 721.31.15 31.211 significant condition F: etat significatif S: estado significativo; condicion significativa Condition of a signal element defining the meaning of that signal element, in accordance with a code. Note - This condition can be a function of the value of the signal element e.g. amplitude, frequency, phase or a combination of these. 721.21.22 31.22 significant interval F: intervalle significatif S: intervalo significativo Time interval between two consecutive significant instants. 721.21.30 31.23 theoretical duration of a significant interval F: duree theorique d'un intervalle significatif S: duracion teorica de un intervalo significativo The exact duration prescribed for a significant interval. Note - In determining this duration, the standardized and, where necessary, the mean modulation rate has to be taken into account. 721.21.31 31.24 significant instant F: instant significatif S: instante significativo That instant at which a change-over occurs. Note - The instant of change from one significant condition to another. 721.21.29 31.25 restitution delay F: delai de restitution [retard a la restitution] S: retardo de restitucion; retardo en la restitucion Transfer time of a significant instant between a transmitter and the corresponding receiver. 31.26 unit interval F: intervalle unitaire S: intervalo unitario The shortest theoretical duration of a significant interval. Note - In telegraphy the unit interval is the same as the minimal interval. 31.27 modulation rate F: rapidite de modulation S: velocidad de modulacion The reciprocal of the duration of the unit interval or of the shortest theoretical duration of signal element. 721.22.26 31.271 character rate F: rapidite de transfert de caracteres S: velocidad de caracteres The average number of characters transferred per unit time between two points. 721.22.29 31.272 binary rate F: debit binaire S: velocidad binaria The aggregate rate in a transmission path expressed in bits per second. Note 1 - The transmission rate is given by: i =1 ~ fIi =m [Unable to Convert Formula] 2 | fIn i where m is the number of parallel transmission channels, Ti is the shortest theoretical duration of signal ele- ment for the i th channel expressed in seconds, and ni is the number of significant conditions of the modulation in the i th channel. For a single channel (serial transmission) it reduces to: [Unable to Convert Formula] with two-condition modulation (n = 2), it is 1/T . For a parallel transmission with equal minimum intervals and equal number of significant conditions on each channel, it is: m [Unable to Convert Formula] with two-condition modulation it reduces to m /T . Note 2 - The symbol of the unit of binary rate is bit/s. 721.22.30 31.273 effective character rate F: cadence utile de transfert S: velocidad efectiva de caracteres The average number of binary digits, characters or blocks transferred per unit time between two points and accepted as valid at the reception. 721.22.31 31.274 full character rate In synchronous telegraphy, the maximum number of character signals per unit time achievable in a given synchronous channel. 31.275 half [quarter] character rate Character rate reduced to one half [one quarter] of the full characrer rate by using half [quarter] of the available time in the full rate channel. 31.28 baud (Bd) F: baud (Bd) S: baudio (Bd) The unit of modulation rate; the number of bauds is equal to the reciprocal of the duration in seconds of the shortest signal element or of the unit interval in such signal. Note - For example, if the duration of the unit interval is 20 ms, the modulation rate is 50 bauds. 721.22.27 31.29 isochronous F: isochrone S: isocrono Pertaining to a signal or a time-varying phenomenon character- ized by significant instants separated by time intervals having a duration theoretically equal to the duration of a unit interval or to an integral multiple of this duration. 721.22.01 31.291 anisochronous F: anisochrone S: anisocrono Pertaining to a signal or a time-varying phenomenon character- ized by significant instants separated by time intervals having durations not constrained to be all equal to the duration of a unit interval or to an integral multiple of this duration. 721.22.02 31.30 start-stop telegraph signal F: signal telegraphique arythmique S: se~al telegrafica arritmica A telegraph signal containing sequences of unit elements, each sequence being of equal duration and corresponding to a transmitted character and preceded by a start element and followed by a period of condition Z, the duration of which is not fixed. 721.22.03 31.35 number of significant conditions F: valence S: valencia (numero de estados significativos) Number of different significant conditions that a signal ele- ment can assume in accordance with a code. 721.21.23 31.351 two condition [three condition] [four condition] F: bivalent [etc.] S: bivalente [trivalente] [tetravalente]; de dos estados, etc. A qualifying term indicating that the number of significant conditions used is two [three] [four]. 721.21.24-26 31.37 (For the countries of English language. The English and French terminologies do not correspond.) marking; spacing (see also Definition 31.38) mark; space F: travail; repos S: trabajo, reposo Designation of the two significant conditions of a binary modulation (or restitution). The English term "marking" or "mark" French term 1. In Morse, corresponds to those portions of dot and dash signals that, 1. Travail for example, when actuating a Morse inker, will cause the inker to mark the paper. 2. In printing telegraphy, corresponds to the significant condition that 2. Repos or travail results in an active selecting operation in a receiving apparatus. according to the system Note 1 - In start-stop automatic transmission, the term corresponds idem to the perforation of a hole in the tape. Note 2 - In standardized start-stop telegraphy the term corresponds Repos to the "stop" element. 3. In isochronous systems, the term that is arbitrarily assigned to one 3. Repos or travail or the other of the two signalling conditions. according to the system The English term "spacing" or "space" 1. In Morse, corresponds to the spaces separating marking signals and 1. Repos to the spaces separating complete characters. 2. In printing telegraphy, corresponds to the significant condition that 2. Travail or repos results in a passive selecting operation in a receiving apparatus. according to the system French term Note 1 - In start-stop automatic transmission the term corresponds Travail or repos to the absence of perforation in the tape. accord- ing to the system Note 2 - In standardized start-stop telegraphy the term corresponds Travail to the "start" element. 3. In isochronous systems, the term that is assigned to the non-marking 3. Travail or repos signalling condition. according to the system The CCITT has recommended that those terms should not be used in telegraph circuit diagrams, but that the letters A and Z should be used to represent the two significant conditions of a binary modulation (see Definition 31.38). The French term "travail" applies to the significant condition that: English term 1. In Morse corresponds to the recording of an impression on the paper; 1. Mark 2. In International Telegraph Alphabet No. 2, corresponds to the "start" 2. Space element of a start-stop signal and to the absence of per- foration in the tape in start-stop automatic transmission. The French term "repos" applies to the significant condition that: 1. In Morse corresponds to spaces; 1. Space 2. In International Telegraph Alphabet No. 2, corresponds to the "stop" 2. Mark element of a start-stop signal and to the perforation of the tape in start-stop automatic transmission. 31.38 position A, position Z F: position A, position Z S: posicion A, posicion Z Representation of the positions occupied by the moving parts (for example, relay armatures) in a circuit diagram. 1 In a diagram representing a complete telegraph connec- tion, operated by binary modulation, the positions that all the moving parts in the connection should simultaneously occupy, so that the electro-magnet of the receiver shall be in a given posi- tion (A or Z), should be designated in the same way as this posi- tion. 2 Position A is that which corresponds to the start signal of a standardized start-stop apparatus: position Z is that which then corresponds to the stop signal. 3 In the case of a point-to-point start-stop circuit, the moving parts should all be shown in position Z. 4 In the case of a diagram of a switched connection, the moving parts should all be shown in the position corresponding to the free condition of the circuits. Thus, for example, in the standardized international telex system, the position in question is A. 31.381 A (Z) condition F: etat A (Z) S: estado A (o estado Z) The significant condition of a start element (stop element) in start-stop transmission. Note - For other representations see the table of equivalence in Recommendation V.1. 721.22.19 31.3811 A (Z) element F: moment A (Z) S: elemento A (o elemento Z) In a code combination, a unit element to which is assigned the A (Z) condition. 721.22.24-25 31.3812 idle circuit condition F: etat de repos (d'un circuit) S: estado de circuito en reposo The characteristic state of the circuit in an established con- nection when it is transmitting neither character signals nor supervisory signals. 721.33.56 31.39 unit element F: element unitaire S: elemento unitario A signal element having a duration equal to the unit interval. 721.21.33 31.40 reversals Uninterrupted sequence of signal elements of a two condition signal with alternating significant conditions all of the same duration and equal to that of the unit interval. 31.401 1 | | reversals Periodical signals in which every significant interval is equal to the unit interval. 31.41 m | | pattern An uninterrupted sequence of binary signal elements of which the significant conditions alternate between m and n unit interval durations. 31.42 Morse code F: code Morse S: codigo Morse A two-condition telegraph code in which characters are represented by groups of dots and dashes, these groups being separated by spaces. 721.31.25 31.43 dot (in Morse code) F: point (en code Morse) S: punto (en codigo Morse) A signal element of mark condition and of duration of one unit interval followed by a signal element of space condition having a nominal duration of one unit interval. 721.31.28 31.44 dash (in Morse code) F: trait (en code Morse) S: raya (en codigo Morse) A signal element of mark condition and of a duration of three unit intervals followed by a signal element of space condition hav- ing a nominal duration of one unit intervals. 721.31.29 31.45 space (between characters and words in Morse code) F: espace (entre deux caracteres, deux mots en code Morse) S: espacio (entre caracteres y entre palabras, en codigo Morse) A signal element of space condition and nominal duration of two unit intervals between characters and six unit intervals between words. 721.31.30 31.451 space condition (in Morse code only) F: repos (en code Morse) S: reposo (en codigo Morse) Designation given to one of the two significant conditions in Morse code, the other condition being designated "mark". 721.31.27 31.452 mark condition (in Morse code only) F: travail (en code Morse) S: trabajo (en codigo Morse) Designation given to one of the two significant conditions in Morse code. 721.31.26 32 SERIES - TELEGRAPH CHANNELS 32.01 telegraph channel F: voie de transmission telegraphique S: canal telegrafico A means of transmission of telegraph signals in one direction between two points. Note 1 - A telegraph channel may be characterized by the number of significant conditions, by the nominal modulation rate and by the code format it is designed to admit. Example: A 50 baud channel for two-condition modulation. Note 2 - Several telegraph channels may share a common path; for example each channel is allocated a particular frequency band or particular time slot. 721.33.01 32.011 complete telegraph channel F: voie telegraphique complete S: canal telegrafico completo A telegraph channel between two terminal sets. Note - A retransmitter with storage of signals is considered as a terminal set and terminates a complete channel. 721.33.03 32.012 sub-channel F: sous-voie S: subcanal A tributary channel which is allocated a proportion of a stan- dard channel rate. Example: A transmission channel obtained by time-division and which is allocated a submultiple of an actual character transfer rate of a standard channel. 721.33.51 32.014 multiple channel F: multivoie S: multicanal Pertaining to or designating a telegraph transmission system in which two or more channels are used for transmission of a char- acter signal propagating in the same direction between the same two points. 721.33.21 32.015 transmit channel F: voie d'emission S: canal de emision The designation at a terminal or other equipment, of a channel used for transmitting. 721.33.09 32.016 receive channel F: voie de reception S: canal de recepcion The designation at a terminal or other equipment, of a channel used for receiving. 721.33.10 32.017 serial transmission F: transmission serie S: transmision serie Transmission of the signal elements of a telegraph signal at successive time intervals, either contiguous or not. 721.33.16 32.018 parallel transmission F: transmission parallele S: transmision paralelo The simultaneous transmission of the signal elements of a telegraph character signal on separate channels. 721.33.17 32.019 start-stop transmission F: transmission arythmique S: transmision arritmica A transmission process using start-stop signals. 721.22.07 32.0110 synchronous transmission F: transmission synchrone S: transmision sincrona Transmission using isochronous signals in which the sending and receiving instruments are operating continuously in a constant time difference between corresponding significant instants. 721.22.05 32.0111 synchronous system F: telegraphie synchrone S: sistema sincrono A system of alphabetic telegraphy using synchronous transmis- sion. 721.31.17 32.0112 element synchronism F: synchronisme elementaire S: sincronismo de los elementos In synchronous transmission, the condition in which the rate of the local timing coincides completely with the rate of the received signal elements. 721.33.43 32.0113 element synchronization F: synchronisation elementaire S: sincronizacion de los elementos The action of adjustment of element synchronism. 721.33.44 32.0114 code independent channel F: voie independante du code S: canal independiente del codigo Telegraph channel capable of transmitting telegraph signals irrespective of the code used. 721.51.31 32.0115 code dependent channel F: voie dependante du code S: canal dependiente del codigo A telegraph channel capable of transmitting telegraph signals only in a specified n-unit code format. 32.0115bis | fBsubchannel In synchronous telegraphy a channel having a sub-multiple of the full character rate. 32.0116 transparency F: transparence S: transparencia Possibility to transmit any telegraph signal with the only condition that a specified modulation rate cannot be exceeded. 32.02 telegraph circuit F: circuit telegraphique S: circuito telegrafico A pair of associated telegraph channels permitting transmis- sion in both directions between two points. 721.33.04 32.06 telegraph repeater F: translation (telegraphique) S: repetidor (traslator) telegrafico A device which can receive telegraph signals and immediately retransmit them with the same meaning on the next line section. 721.33.11 32.071 modulation converter F: translation convertisseuse de modulation S: convertidor de modulacion A telegraph repeater in which the input and output signals are represented with the same code, but use different types of modula- tion. 721.33.13 32.08 code converter F: convertisseur de code S: convertidor de codigo Telegraph repeater which can accomplish a code conversion. 721.34.52 32.081 speed conversion F: conversion de rapidite S: conversion de velocidad The conversion of the modulation rate of the received signal to a different modulation rate suitable for the subsequent equip- ment. 721.22.28 32.09 broadcast repeater F: translation pour diffusion S: repetidor de difusion A repeater connecting several channels, one incoming and the other outgoing. 32.10 conference repeater F: translation pour conference S: repetidor para conferencias A telegraph repeater connecting several circuits, which receives signals from any one of the circuits and automatically retransmits them over all the others. 32.11 telegraph regenerative repeater F: regenerateur (telegraphique) S: repetidor regenerativo telegrafico A telegraph repeater designed to retransmit signals free from telegraph distortion. 721.33.12 32.12 direct current transmission F: transmission par courant continu S: transmision en corriente continua A form of transmission of telegraph signals where significant conditions are effected by the direct application of voltages sup- plied from direct current sources. 721.24.01 32.13 single current transmission F: transmission par simple courant S: transmision a simple polaridad (por corriente sim- ple) Direct current transmission effected by applying voltages of the same polarity, producing currents of the same direction. 721.24.02 32.131 on-off transmission F: transmission par tout ou rien S: transmision cerrado-abierto A two-condition single current transmission where one signifi- cant condition is represented by applied zero voltage and no current in the circuit. 721.24.04 32.14 double current transmission F: transmission par double courant S: transmision a doble polaridad (por corriente doble) A form of two-condition direct current transmission effected by applying to a wire two voltages of opposite polarity, producing currents of opposite directions. 721.24.03 32.15 closed-circuit working F: transmission par fermeture de circuit ou par envoi de courant S: funcionamiento en circuito cerrado Single-current transmission in which a current flows in the circuit while the transmitting device is at rest. 32.16 open-circuit working F: transmission par ouverture (rupture) de circuit ou par interruption de courant (par batterie centrale) S: funcionamiento en circuito abierto Single-current transmission in which no current flows in the circuit while the transmitting device is at rest. 32.17 simplex; half duplex (deprecated) F: simplex; a l'alternat; semi-duplex (deconseille dans ce sens) S: simplex; semiduplex (desaconsejado) Designating or pertaining to a mode of operation or the equip- ment concerned, by which information can be transmitted in either direction but not simultaneously, between two points. 721.23.15 32.18 duplex; full duplex (deprecated) F: duplex; bilateral simultane S: duplex; duplex completo (desaconsejado) Designating or pertaining to a mode of operation or the equip- ment concerned, by which information can be transmitted in both directions simultaneously between two points. 721.23.16 32.26 unidirectional F: unilateral S: unidireccional Pertaining to a link where the transfer of the user's informa- tion can occur in one preassigned direction only. 721.23.21 32.28 carrier transmission F: transmission par courants porteurs S: transmision por portadoras A transmission in which the telegraph signals from a transmitter modulate an alternating current. 721.25.01 32.29 amplitude modulation F: modulation d'amplitude S: modulacion de amplitud In telegraphy, modulation in which the significant conditions are represented by alternating currents of different amplitude. 721.25.05 32.30 frequency modulation F: modulation de frequence (ou modulation en frequence) S: modulacion de frecuencia In telegraphy, modulation in which the significant conditions are represented by alternating currents of different frequency. Note - The representative function of the modulation signal may be continuous or discontinuous at the significant instants. 32.301 characteristic frequency Frequency corresponding to a significant condition. 32.302 mean dynamic frequency In a FMVFT system the mean frequency at the modulator output when reversals are applied to its input. 32.303 mean static frequency In a FMVFT channel the mean value of the actual characteristic frequencies of that channel. 32.304 compensation for frequency drift Elimination of the effect of frequency drift on inherent tele- graph distortion. 32.31 frequency shift keying (FSK); frequency shift modula- tion F: modulation par deplacement de frequence; (MDF) S: modulacion por desplazamiento de frecuencia (MDF) Phase continuous frequency modulation in which the frequency of a periodic sinusoidal oscillation is varied between a set of discrete values, each value representing a significant condition of a modulating telegraph signal. 721.25.06 32.311 telegraph discriminator F: discriminateur telegraphique S: discriminador telegrafico A device for converting frequency shift telegraphy signals into direct current transmission signals. 721.34.55 32.312 phase shift keying (PSK); phase shift modulation F: modulation par deplacement de phase (MDP) S: modulacion por desplazamiento de fase Telegraph transmission by phase modulation in which each change from one significant condition to another is characterized in steady-state by specified changes of phase of the oscillatory source or of the sinusoidal wave. 721.25.07 32.32 frequency-exchange modulation; two tone modulation F: modulation par mutation de frequences S: modulacion por cambios opuestos de frecuencia; modulacion de dos frecuencias A frequency modulation method in which the change from one frequency to another is not necessarily phase continuous. 32.34 multiplex F: multiplex S: multiplex Designating or pertaining to an installation in which a common transmission channel is divided into several separate channels each capable of transmitting signals independently in the same direc- tion. 721.23.04 32.341 multiplexing F: multiplexage S: multiplexacion; multiplexion A process for combining signals from several separate tribu- tary channels for transmission in the same direction over a common bearer channel. 721.23.05 32.3410 tributary channel F: voie affluente S: canal afluente An individual input channel to a multiplexer. 32.3411 branch line multiplex A multiplex whose capacity is a submultiple of that of a main multiplex and which gives the possibility to group a certain number of channels of the latter in order to extend or divert them into a specific direction with the aim, for example, to connect a small group of subscribers. 32.3412 bearer Common means of transmission e.g. common channel or bit stream used for a multiplexer. 32.3413 submultiplex A multiplex whose bearer is part of a higher-order multiplex. 32.3414 equipped channel A channel having all the necessary equipment to enable usage in case of need. 32.3415 allocated channel A channel used in forming a subscriber line, a link or a cir- cuit. 32.3416 hybrid multiplex A multiplex providing simultaneously transparent and non-transparent (code-and-speed independent and dependent) chan- nels. 32.342 demultiplexing F: demultiplexage S: demultiplexacion; demultiplexion A process applied to a multiplex signal for recovering signals combined within it and for restoring the distinct individual chan- nels of these signals. 721.23.06 32.343 multiplexer F: multiplexeur S: multiplexor An equipment which combines a number of tributary channels onto a fewer number of aggregate bearer channels, the relationship between the tributary and aggregate channels being fixed. 721.23.07 32.344 demultiplexer F: demultiplexeur S: demultiplexor An equipment for effecting demultiplexing. 721.23.08 32.345 muldex F: muldex S: muldex An equipment which combines/separates a number of tributary circuits onto/from a fewer number of aggregate bearer circuits, the relationship between the tributary and aggregate circuits being fixed. 721.23.09 32.3451 muldex/concentrator A muldex with the line concentrating function ensuring that tributary channels are only allocated time slots in the aggregate bit stream for the duration of their seizure. 32.346 homogeneous multiplex F: multiplex homogene S: multiplex homogeneo A multiplex in which all the individual channels are for the same modulation rate. Note - In addition to the modulation rate it is sometimes necessary to define conditions for all channels such as the charac- ter length. 721.23.13 32.347 heterogeneous multiplex F: multiplex heterogene S: multiplex heterogeneo A multiplex in which all the individual channels are not for the same modulation rate or character rate, etc. Note - For the signalling rate condition we can add addi- tional conditions. 721.23.14 32.348 homogeneous structure F: structure homogene S: estructura homogenea Pertaining to a group of individual channels in a multiplex system all of which have the same properties, e.g. modulation rate, character format, inherent telegraph distortion. 32.349 aggregate signal F: signal composite S: se~al global; se~al compuesta; se~al multiplexada Signal transmitted over the common multiplex channel. 721.23.10 32.3491 filling bit Bit with no specific meaning used to fill a time of communica- tion during which there are no significant bits to be transmitted. 32.35 time division multiplexing (TDM) F: multiplexage par repartition dans le temps (MRT); multiplexage temporel S: multiplexacion por division en el tiempo (MDT); multiplexacion temporal; multiplexion temporal Multiplexing in which a separate periodic time interval is allocated to each tributary channel in the common channel. 721.23.11 32.3502 element [character] interleaving In a multichannel system with time division, the forming of a cycle containing one element [character] from each channel. 32.351 frame F: trame S: trama A repetitive set of consecutive timeslots constituting a com- plete cycle of a signal in which the relative position of each timeslot in the cycle can be identified. Example: In a time division multiplex system with a binary aggregate signal a frame is the smallest periodically repeated bit group containing bits from all individual channels together with bits carrying auxiliary information. 721.25.21 32.3511 frame slot An elementary time interval generally allocated to tributary channel. 32.3512 frame structure General rule of the establishment of a frame with allocation of each bit to a determined channel. 32.352 subframe F: sous-trame S: subtrama A fixed number of time slots within a frame, which comply with the definition of a frame, but constitute a shorter cycle than the original frame. 721.25.22 32.353 frame alignment F: verrouillage de trame S: alineacion de trama The state in which the frame generated by the receiving equip- ment has a desired constant phase relationship with the frame of the received signal, so that the individual timeslots in each frame can be uniquely identified. 721.25.23 32.354 frame resynchronization F: resynchronisation de trame S: resincronizacion de trama The act of re-establishing lost frame alignment. 32.355 synchronization bit F: bit de synchronisation S: bit de sincronizacion; bit de sincronismo A binary digit which is used for frame synchronization. 721.33.45 32.3551 synchronization word Sequence of bits allocated to synchronization and appearing periodically in one or a fixed number of consecutive fundamental frames. 32.3552 synchronization frame Sequence of a fixed number of consecutive fundamental frames containing one synchronization word. 32.356 character-interleaved transmission F: transmission multiplex a caracteres entrelaces S: transmision con entrelazado de caracteres Time-division multiplex telegraphy in which characters are transmitted sequentially on a common channel, the characters coming from each independent channel in turn without separation of the unit elements of each character. 721.33.27 32.357 bit-interleaved transmission F: transmission multiplex a moments entrelaces S: transmision con entrelazado de bits Time-division multiplex telegraphy in which the signal ele- ments of each character signal are transmitted on the common chan- nel separated by signal elements belonging to other characters com- ing from different channels. 721.33.28 32.358 character cycle F: cycle de caractere S: ciclo de caracter The period in which each tributory channel of a time-division multiplex has completed one character in the common channel. 721.33.42 32.36 frequency division multiplexing (FDM) F: multiplexage par repartition en frequence (MRF) S: multiplexacion por division de frecuencia (MDF); multiplexion por division de frecuencia Multiplexing in which a separate frequency band is allocated to each tributary channel in common channel. 721.23.12 32.37 voice frequency telegraphy (VFT) F: telegraphie harmonique; telegraphie a frequences vocales S: telegrafia armonica (TA) Carrier telegraphy in which the frequency band of the modu- lated alternating current lies in the telephone frequency band. 721.33.22 32.371 multi-channel voice-frequency telegraphy (MCVFT) F: telegraphie harmonique S: telegrafia armonica multicanal (TAMC) A telegraph transmission within a telephone type channel using frequency-division multiplexing. 721.33.22 32.372 single channel voice frequency telegraphy (SCVFT) F: telegraphie harmonique a une voie S: telegrafia armonica monocanal Voice frequency telegraphy providing a single telegraph chan- nel in a telephone type channel. Note - The term SCVF is usually applied to a telegraph cir- cuit (32.02) rather than to a telegraph channel (32.01). 32.373 telephone-type channel F: voie de type telephonique S: canal de tipo telefonico A transmission channel of characteristics suitable for the transmission of speech but which is used for the transmission of other signals. 721.23.01 32.374 telephone-type circuit F: circuit de type telephonique S: circuito de tipo telefonico A pair of associated telephone-type channels permitting transmission in both directions between two points. 721.23.02 32.38 voice frequency multiplex aggregate F: faisceau de telegraphie harmonique S: haz de circuitos de telegrafia armonica The set of voice-frequency multiplex telegraph circuits simul- taneously accommodated in a telephone type channel. 721.33.23 32.49 phantom circuit F: circuit fant | me S: circuito fantasma An additional circuit derived from the conductors of two metallic circuits, with the two conductors of each metallic circuit effectively being used in parallel. Example: A telegraph circuit superposed on two telephone cir- cuits. 721.24.06 32.50 earth-return phantom circuit F: circuit approprie; circuit telegraphique fant | me avec retour par la terre S: circuito fantasma con vuelta por tierra An additional circuit derived from the conductors of a metal- lic circuit, with these two conductors effectively being used in parallel, and with return through the earth or the sea between the end points. Example: A telegraph circuit superposed on a telephone cir- cuit, with earth-return. 721.24.07 32.51 earth-return double phantom circuit F: (circuit) approprie de fant | me; (circuit) approprie de combine; circuit telegraphique superfant | me avec retour par la terre S: circuito superfantasma con vuelta por tierra An additional earth-return circuit derived from two pairs of metallic conductors used in parallel. 721.24.08 32.52 double phantom circuit F: circuit superfant | me S: circuito superfantasma An additional circuit derived from the conductors of two phan- tom circuits, with the four conductors of each phantom circuit effectively being used in parallel. 721.24.09 32.55 interband telegraphy F: telegraphie interbandes S: telegrafia interbanda A form of carrier transmission in which the telegraph channel is situated in a narrow band between two telephone channels. 721.25.14 32.56 intraband transmission F: telegraphie intrabande S: telegrafia intrabanda A carrier telegraphy in a narrow band of frequencies appropri- ated inside the frequency band of a telephone channel to permit simultaneously a telephone transmission and a transmission by a discretely-timed signal. 721.25.15 32.57 speech plus simplex (S + S) equipment F: equipement univocal S: equipo telefonia mas simplex; equipo T + S Equipment for intraband telegraphy providing a simplex tele- graph circuit by the use of a single telegraph carrier frequency. 721.25.16 32.58 speech plus duplex (S + D) equipment F: equipement bivocal S: equipo telefonia mas duplex; equipo T + D Equipment for intraband telegraphy providing a duplex tele- graph circuit by the use of two telegraph carrier frequencies. 721.25.17 32.61 nominated reserved circuit F: circuit de secours (pour la telegraphie harmonique) S: circuito de reserva especializado A circuit, normally available for telephone traffic, which is allocated for the operation of a multi-channel telegraph system when the main, or primary, circuit becomes faulty. 721.33.15 32.631 Baudot telegraphy F: telegraphie Baudot S: telegrafia Baudot Synchronous telegraphy, generally character interleaved teleg- raphy, using the International Telegraph Alphabet No. 1. 721.33.29 32.632 Van Duuren radiotelegraph system; teleprinting over radio circuits (TOR) F: radiotelegraphie Van Duuren; TOR (teleprinting over radio circuits) S: sistema de radiotelegrafia Van Duuren A radiotelegraphy system with correction by repetition, in general time-division multiplex in two or four channels and using the Van Duuren code. Note - The main characteristics are defined in Recommenda- tion 342-2 of CCIR, Geneva 1982. 721.33.30 32.633 signal repetition F: signal de repetition S: se~al de repeticion A function signal which is used in an error detecting and feedback system to request a repetition or to precede a retransmis- sion. Note - In the International Telegraph Alphabet No. 3 this signal corresponds to the code combination AZZAZAA. 721.27.35 32.634 repetition cycle F: cycle de repetition S: ciclo de repeticion A sequence of characters, the minimum number of which is determined by the loop time-delay of an error detecting and feed-back system. This delay is necessary to provide automatic repetition of information. 721.27.36 32.635 RQ cycle; request cycle F: cycle RQ; cycle de demande S: ciclo RQ; ciclo de peticion The repetition cycle requested in an error detecting and feed- back system when a multilation is detected. Note - See CCIR Recommendation 342-2. 721.27.37 32.636 BQ cycle; response cycle F: cycle BQ; cycle de reponse S: ciclo BQ; ciclo de respuesta The repetition cycle transmitted in an error detecting and feedback system when signal repetition is received. Note - See CCIR Recommendation 342-2. 721.27.38 32.637 non-print cycle F: cycle sans impression S: ciclo sin impresion The operating time of a receiver in an error detecting and feedback system, initiated by the detection of a mutilation or by a signal repetition that has the same duration as a repetition cycle and during which all signals received are prevented from producing printing. Note - See CCIR Recommendation 342-2. 721.27.39 32.638 gated RQ F: pointage de RQ S: punteado de RQ A procedure in which a check is made for the presence of a signal repetition during the non-print cycle. Note - See CCIR Recommendation 342-2. 721.27.40 32.639 tested RQ F: contr | le de RQ S: control de RQ; prueba de RQ A procedure in which a check is made for the presence of a signal repetition and for the ratio of the number of elements A to the number of elements Z in each of the characters received after the signal repetition within the non-print cycle. Note - See CCIR Recommendation 342-2. 721.27.41 32.640 testing repetition cycle F: cycle de repetition contr | le S: ciclo de repeticion controlado A non-print cycle in which a check is made for the presence of a signal repetition and for the correct ratio of the number of ele- ments A to the number of elements Z in all the characters received. Note - See CCIR Recommendation 342-2. 721.27.42 33 SERIES - QUALITY OF TELEGRAPH TRANSMISSION 33.01 perfect signal F: signal parfait S: se~al perfecta A telegraph signal such that all the significant intervals are associated with correct significant conditions and conform accu- rately to their theoretical durations. 721.26.01 33.02 ideal instant F: instants ideals S: instante ideal The instant with which the significant instant (if existing) would coincide in certain conditions to be specified for each par- ticular case. Note - It will be necessary to indicate, in each particular case, how these ideal instants are determined. a) Start-stop signal The ideal instant associated with the start element is the instant at which this element begins. The ideal instant associated with each of the other elements is n times the theoretical unit interval later than the ideal instant of the start element of the same signal, n being the rank of this element in the signal. The standardized unit interval should be taken as the theoret- ical unit interval. The interval corresponding to the real mean modulation rate can also be taken, provided that it is specified. The instant corresponding to the beginning of the start ele- ment of a signal should be known as the reference ideal instant for this signal. b) Isochronous signal An ideal reference instant can be chosen arbitrarily. All the others are deduced from it by intervals equal to the corresponding theoretical significant intervals. In the absence of any other deciding reason, the reference ideal instant shall be chosen so that the mean value of the devia- tions with respect to it is equal to zero. 721.26.02 33.03 incorrect signal F: signal incorrect S: se~al incorrecta A telegraph signal in which the significant conditions of one or more elements differ from the kind prescribed by the code. 721.26.04 33.04 telegraph distortion; time distortion F: distorsion telegraphique S: distorsion telegrafica The undesired effect on a telegraph signal, when the signifi- cant instants do not coincide with the corresponding ideal instant. Note - A telegraph signal suffers from telegraph distortion when the significant intervals have not all exactly their theoreti- cal durations. 721.26.03 33.041 transmitter distortion F: distorsion a l'emission S: distorsion en la emision; distorsion en el emisor The telegraph distorsion of a transmitter measured at the out- put under specified standard conditions. 721.26.19 33.06 degree of individual distortion (of a particular sig- nificant instant) F: degre de distorsion individuelle (d'un instant sig- nificatif) S: grado de distorsion individual (de un instante sig- nificativo determinado) The ratio of the algebraic value of the displacement in time of a given significant instant from the corresponding ideal instant, to a specified unit interval. Note 1 - By convention the displacement is considered posi- tive when the significant instant occurs after the ideal instant, and conversely it is considered negative when it occurs before. Note 2 - The degree of individual distortion is usually expressed as a percentage. 721.26.05 33.061 early distortion Telegraph distortion characterized by the fact that a signifi- cant instant appears earlier than the corresponding ideal instant. 33.062 late distortion Telegraph distortion characterized by the fact that a signifi- cant instant appears later than the corresponding ideal instant. 33.07 degree of isochronous distortion F: degre de distorsion isochrone S: grado de distorsion isocrona 1) Ratio of the maximum measured difference, irrespective of sign, between the actual and the theoretical intervals separating any two significant instants, these instants not necessarily being consecutive, to the mean unit interval. 2) The algebraic difference between the highest and the lowest value of the degree of individual distortion referred to the mean duration of the unit interval for the significant instants of an isochronous signal. The degree of distortion is expressed as a percentage. Note - The result of the measurement should be completed by an indication of the period, usually limited, of the observation. For a prolonged modulation (or restitution) it will be appropriate to consider the probability that an assigned value of the degree of distortion will be exceeded. 721.26.06 33.08 degree of start-stop distortion F: degre de distorsion arythmique S: grado de distorsion arritmica 1 In start-stop transmission the ratio of the maximum measured difference, irrespective of sign, between the actual and theoreti- cal intervals separating any significant instant from the signifi- cant instant of the start element immediately preceding it, to the unit interval. 2 The highest absolute value of the degrees of individual dis- tortion of the significant instants of a start-stop signal which is reached within a specified time interval. The degree of distortion of a start-stop modulation, restitu- tion or signal is usually expressed as a percentage. Note 1 - The result of the measurement should be completed by an indication of the period, usually limited, of the observation. For a prolonged modulation (or restitution) it will be appropriate to consider the probability that an assigned value of the degree of distortion will be exceeded. Note 2 - By convention the start-stop distortion may be con- sidered positive when the significant instant occurs after the ideal instant and conversely, negative when it occurs before. 721.26.07 33.09 degree of gross start-stop distortion F: degre de distorsion arythmique global S: grado de distorsion arritmica global The degree of start-stop distortion determined when the assumed unit interval is exactly that appropriate to the nominal modulation rate. Note - By convention the gross start-stop distortion may be considered positive when the significant instant occurs after the ideal instant and conversely, negative when it occurs before. 721.26.08 33.10 degree of synchronous start-stop distortion; degree of start-stop distortion at the actual mean modulation rate F: degre de distorsion arythmique au synchronisme ; degre de distorsion arythmique a la rapidite reelle moyenne S: grado de distorsion arritmica en el sincronismo ; grado de distorsion en el sincronismo a la velocidad media real de modulacion The degree of start-stop distortion determined when the assumed unit interval is that appropriate to the actual mean modu- lation rate. Note 1 - In practice the degree of synchronous start-stop distortion is measured by adjusting the scanning rate of the dis- tortion measuring set. Note 2 - As for Definition No. 33.07. Note 3 - For the determination of the actual mean modulation rate, account is only taken of those significant instants of modu- lation (or restitution) that correspond to a change of condition in the same sense as that occurring at the beginning of the start ele- ment. 721.26.09 33.12 degree of standardized test distortion F: degre de distorsion d'essai normalise S: grado de distorsion normalizado de prueba The degree of individual distortion of the received signal measured during a specified period of time when the signal at the sending end is perfect and corresponds to a specified text. 721.26.10 33.13 inherent distortion (of a transmission channel) F: distorsion propre S: distorsion propia (de un canal de transmision) The telegraph distortion of a received signal at the output of a transmission channel when the signal at the input is a perfect signal. Note 1 - The inherent distortion includes all the distortions produced in the channel such as bias distortion, characteristic distortion and fortuitous distortion. Note 2 - The concept of inherent distortion can be extended to the constituents such as a telegraph relay, telegraph repeater or exchange. 721.26.11 33.14 conventional degree of distortion F: degre conventionnel de distorsion S: grado convencional de distorsion The degree of individual distortion which has a very small assigned probability of being exceeded over a prolonged period of time. 721.26.17 33.15 characteristic distortion F: distorsion caracteristique S: distorsion caracteristica The telegraph distortion caused by transients which are pro- duced by the transmission of the signal in a transmission channel of specific characteristics. Note - Characteristic distortion is a function of the form of the input signal. 721.26.14 33.151 characteristic distortion compensation Suppression of characteristic distortion on signal restitution by shifting the decision level of this restitution in accordance with the preceeding sampling result. 33.16 fortuitous distortion F: distorsion fortuite; [distorsion irreguliere]; [distor- sion accidentelle] S: distorsion fortuita The telegraph distortion resulting from random events affect- ing the channel or equipments and such that the degree of indivi- dual distortion of any significant instant is unpredictable. 721.26.15 33.17 bias distortion F: distorsion biaise S: distorsion asimetrica The telegraph distortion effecting a two-condition telegraph signal when the mean degrees of individual distortion are different from the two directions of change-over. 721.26.12 33.18 cyclic distortion F: distorsion cyclique S: distorsion ciclica A telegraph distortion which is due to events having a periodic character such that the degrees of individual distortion themselves show a periodic character in the sequence of the signi- ficant instants. 721.26.16 33.181 distortion metter Equipment for measuring telegraph distortion. 33.182 distortion analyser Distortion meter for statistical measurements of the degree of individual distortion. 33.19 element [character] error rate Ratio of the number of elements [characters] incorrectly received to the total number of elements [characters] correctly emmitted. Note - In determining the quality of transmission it is pos- sible to consider the probability of exceeding a given error rate. 33.23 efficiency factor in time (of a transmission with automatic repetition for the correction of errors) F: facteur d'efficacite dans le temps (d'une transmission avec correction d'erreurs par repetition) S: factor de eficacia (o eficacia) en el tiempo (de una transmision con correccion de errores por repeticion automatica) Ratio of the time necessary to transmit a text automatically without repetition, at a specified modulation rate, to the time actually taken to receive the same text with error control by repetition for a given error rate. Note - The actual conditions in which the measurement is made should be specified, in particular the duration of the measurement. 721.27.34 33.24 mutilation F: mutilation S: mutilacion A defect such that a signal element becomes changed from one significant condition to another. 721.27.01 33.25 regeneration Elimination of telegraph distortion. 33.251 inherent regeneration Regeneration resulting from the method of switching or transmission. 33.252 transfer delay Duration between the beginning of transmission and complete reception of a signal. 33.26 controlling station (on a circuit) F: station directrice (sur un circuit) S: estacion directora (de un circuito) A station located on the circuit and having the responsibility for the quality of transmission on the circuit. 33.261 system control station F: station directrice (dans un systeme) S: estacion directora de sistema A terminal station of a multichannel system which is responsi- ble for maintenance and clearance of faults on the system. 721.52.56 33.27 sub-control station F: station sous-directrice S: estacion subdirectora A station, located on the circuit, responsible to the control- ling testing station, and having responsibility for the quality of transmission on the section of the circuit within its territory. 33.29 test section F: section d'essais S: seccion de pruebas The section of a channel that is contained between two sta- tions having measuring equipment enabling tests of telegraph transmission to be made. 33.30 loopback Connection of the forward channel with the corresponding back- ward channel to enable the observation on the backward channel of signals which have been emitted on the forward channel in order to check the quality of transmission. 33.31 error correction by detection and repetition (ARQ) F: correction d'erreurs par detection et repetition (ARQ) S: correccion de errores por deteccion y repeticion Error correction using an error detecting code in which every mutilation discovered at the receiving end causes the sending to the transmitting end, over the return channel, of a function signal which orders the repetition of a fixed sequence of the last signals sent. 721.27.21 33.32 precorrection F: precorrection S: precorreccion Application of an artificial telegraph distortion to signals at the sending end of a channel, in order to completely or partly compensate for the effect of the characteristic distortion of this channel. 721.27.43 33.33 error detecting code F: code detecteur d'erreurs S: codigo detector de errores A redundant code in which the rules of construction are such that any error causing departures from this construction can be automatically detected. 721.27.27 33.35 error correcting code F: code de correction des erreurs S: codigo corrector de errores An error detecting code which also permits the automatic correction of a proportion of the detected errors without using a backward channel. 721.27.28 33.57 transmission plan In a telegraph network a set of limiting values of telegraph distortion and receiver margin compatible with the satisfactory transmission quality of the network. SECTION 10 AVAILABILITY AND RELIABILITY OF INTERNATIONAL TELEGRAPH CIRCUITS Recommendation R.150 AUTOMATIC PROTECTION SWITCHING OF DUAL DIVERSITY BEARERS (Malaga-Torremolinos, 1984; amended at Melbourne, 1988) The CCITT, considering (a) that Recommendation R.54 lays down a character error rate objective for telegraph communication; (b) Recommendation M.201 concerning transmission path restora- tion for service protection; (c) that the availability and reliability of international telegraph transmission may be improved by providing automatic pro- tection switching of dual, diversely routed bearers to carry TDM aggregates conforming to Recommendation R.101; (d) that the principle of automatic switching between dual diversity routed bearers may also apply to other telegraph channel multiplexers such as TDM systems conforming to Recommendation R.111 or frequency-modulated voice frequency telegraph (FMVFT) systems conforming to Recommendation R.35, etc., unanimously declares the following view 1 It may be desirable to take measures to protect the quality and availability of derived international telegraph channels against bearer breaks or degradation, for example: i) where the bearer is prone to relatively frequent interruptions (for example, long-haul bearers in intercontinental relations), such that the provisions of Recommendation R.54 may not be met for a significant proportion of the time; ii) where the number of derived telegraph channels carried on a given telephone-type circuit or other bearer becomes considerable (e.g. in excess of 50). 2 An effective method of counteracting bearer faults is the use of automatic protection switching between dual diversely routed bearers. In this technique, a pair of bearers with geographically diverse paths is selected (e.g. one cable, one satellite), ensuring a low probability of simultaneous outages of both bearers. At the sending end for each direction, the multiplexer aggregate or aggre- gates are connected to both bearers continuously. At the receiving end for each direction, facilities are provided to select automati- cally either of the two incoming aggregate signals, using as cri- teria loss of sync or frame alignment from the TDM or loss of line signal (FMVFT or TDM). 3 Annex A shows methods of implementing protection switching of telegraph bearers. ANNEX A (to Recommendation R.150) Protection switching methods for telegraph aggregates A.1 System configurations A.1.1 Figures A-1/R.150 and A-2/R.150 illustrate simple appli- cations of automatic protection switching between dual, diversely routed telegraph bearers. The aggregate output at each end is transmitted on both bearers continuously. At each end a Bearer Switchover Unit (BSU) automatically (and independently of action at the distant end) selects one of the incoming aggregates from the two bearers and feeds it to the multiplexer (TDM or FMVFT). Figure A-1/R.150, p. Figure A-2/R.150, p. A.1.2 Two of the many further possible configurations using higher order digital multiplexers are shown in block form in Figures A-3/R.150 and A-4/R.150. Figure A-3/R.150, p. FIGURE A-4/R.150, p. A.2 Bearer routing For protection switching to be effective, every effort should be made to diversify the routing of the two bearers. On the inter- national portion, one bearer might be carried by cable and the other by satellite for example. Common equipment needs to be avoided in both the international transmission systems and any relevant national extensions to them. A.3 Bearer switchover unit A.3.1 The BSU splits the multiplexer send path for simultane- ous transmission on both bearers. In the case of TDM, the split will be made before or after the modems as required, i.e. the aggregate signal is split in either its digital or its analogue form. A.3.2 The BSU monitors the appropriate circuit and equipment parameters on the receive path of both bearers. It switches the multiplexer aggregate input from one bearer to the other as fol- lows: The shortening of this delay for Recommendation R.111 TDM aggre- gates is for further study. a) after a continuous period of between one and two seconds when there is: - insufficient signal (where the BSU is in the analogue path) or loss of keying (where the BSU is in the digital path) on the currently selected bearer; and/or - loss of local sync (Recommendation R.101) or frame alignment (Recommendation R.111) within the associated TDM; Note - An optional third condition "the other bearer (the bearer not currently in use) has not been detected as faulty within the previous two seconds" is left for further study. b) once a switchover has occurred, a further switchover due to bearer failure on the newly selected path shall be inhibited for a period of either 8 or 12 seconds and an alarm signal given. A.3.3 When TDM systems are used, the BSU switches the received aggregate signal either in its digital or analogue form. When switching the TDM aggregate in digital form, the follow- ing circuits must also be switched: - received line signal detector (e.g. Recommendation V.24 circuit 109) if required by the TDM; - receiver signal element timing (e.g. Recommendation V.24 circuit 115). A.3.4 The logic controlling the above functions shall be designed to be secure, minimizing the risk of a BSU fault that could affect both bearer paths. _________________________ Advice from the distant TDM that it has lost sync or frame alignment will not of itself cause the BSU to switch over.