1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 (b) that the existence of present terminals and systems utilizing the International Telegraph Alphabet No. 2justifies the provision of a Recommendation for an automatic message switching service;(c) that terminals and systems in use conform to the relevan
2、t CCITT Recommendations;(d) that the application of operational rules in this kind of environment does not preclude the development ofmessaging services, unanimous declaresunanimously declaresthat the following provisions should be applied when a public message switching service is being providedint
3、ernationally for equipment utilizing the International Telegraph Alphabet No. 2.1 General1.1 The format to be used shall comprise a layout with the following basic components: the identification line, the routing line, the origin line. the text.1.2 Length of messagesAs a general rule, the length of
4、messages should not exceed 10 000 printed characters, spaces or separators.Nevertheless, Administrations may establish a different limit by bilateral agreement.1.3 Sequence of signsThe uninterrupted repetition of any sign shall be tolerated up to a number of characters corresponding to aprinted line
5、 varying in length according to the mode of operation used. Beyond this limit, the message shall be refused;subsequent signs forming part of the repetition shall be ignored._1)Formerly numbered F.150 in the Red Book.2 Fascicle II.4 - Rec. F.351.4 RoutingMessages shall be routed on circuits and syste
6、ms in accordance with arrangements and modalities agreedbetween the Administrations concerned.As a rule, each system shall only receive messages for direct retransmission to national users.When difficulties arise in this routing, only the standby circuits and systems previously designated as such sh
7、allbe brought into use. If, however, the standby equipments previously agreed upon prove to be inadequate owing to thespecial nature of the difficulty, the traffic may be routed on other circuits or systems with the prior agreement of theAdministrations concerned or of instances appointed by them fo
8、r the purpose.To avoid critical obstruction of the system or systems used for emergency routing, traffic cannot be deviateduntil the agreement of the Administrations concerned has been obtained; any restrictions placed on the deviation mustbe observed.1.5 Service trafficService traffic exchanged thr
9、ough a system must conform with the example given in 5.2. In all cases, thereference data relating to the original message must appear at the beginning of the text of the service correspondence.These data must in no case be preceded by other information.In cases directly concerned with interworking
10、between systems, the service traffic must be addressed to thesystem itself.1.6 Effects of one system on anotherTraffic between two directly interconnected systems may be affected by the following commands: an order to the partner to stop and then to resume his transmission; a request to repeat messa
11、ges; a request for a load position notice.These commands shall follow the format shown in 5.2 and shall be addressed to the corresponding system.The first word of the text indicates the action to be taken.According to the degree of development of the system, the reaction may be automatic or set off
12、by the operator.1.7 Overloading of systemsPrecautions must be taken against overloading.The system shall signal the moment when a critical load threshold is reached, so that appropriate measures canbe taken before the situation deteriorates further.As far as possible, the system shall complete recep
13、tion of messages in progress before taking action.1.8 Procedure to be applied in the event of total interruption of the systemWhen the interruption is planned (maintenance), the partners shall be notified as far as possible in advance.When it is formally established that a sudden interruption will l
14、ast longer than 2 hours, all the partnersconcerned shall be notified without delay and informed of the measures to be taken or, where applicable, of theapplication of measures planned for the provisional remedy of such system failures.As soon as normal operation of the system is restored, the corres
15、pondents shall be informed without delay.1.9 Period of preservation of archives1.9.1 For automatic accessAn automatic message retransmission system should, as far as possible, be so designed as to allow directaccess, for purposes of repetition or settlement of disputes, to messages transmitted by th
16、e system for at least the past24 hours.Fascicle II.4 - Rec. F.35 31.9.2 For deferred accessArchives relating to the deposit and transmission of messages shall be kept for at least 2 weeks as from the dayfollowing the deposit of the message.1.10 Terminals directly connected to the centre of another A
17、dministrationWhen connection to a national centre cannot be effected, a terminal may exceptionally be connected to thecentre of another Administration, with the consent of the Administrations concerned.1.11 Tolerances1.11.1 At reception, a system must be capable of admitting tolerances whereby recou
18、rse to human interpretation isreduced to a minimum.For maximum efficiency, these tolerances shall, as far as possible, be adapted to the errors most commonlyencountered in operation. Nevertheless, errors liable to interfere with the routing or correct treatment of the messageshall be excluded.Unless
19、 otherwise agreed, messages which cannot be processed, automatically or manually, and charactersequences not recognized as messages shall be notified to the transmitting station by an appropriate message. Thismessage shall be set out in the format described in 5.2 and shall contain in the text the r
20、eferences of the originalmessage (identification line) and the reason for refusal.1.11.2 At transmission, the system must strictly observe the criteria of the agreed format, irrespective of the toleranceadmitted at reception.1.11.3 Departures from these rules may be permitted only with the consent o
21、f the Administrations concerned.2 MessageThe format to be used to prepare a message for transmission is as follows:2.1 Identification lineThe heading of the message is formed by the identification line which comprises:2.1.1. Start-of-message signal (SOM)This signal, normally composed of the sequence
22、 of Combinations Nos. 26, 3, 26, 3 of International TelegraphAlphabet No. 2 (ZCZC or + : + :), may vary according to the mode of operation used. It is followed by the channelserial number.2.1.2 Channel serial numberTransmission numbering shall be applied serially to each point-to-point circuit and e
23、ach terminal using theswitched network. The channel serial number consists of three letters characterizing the circuit (circuit indicator) orterminal used, followed by the order number of the message carried on the circuit, exchanged with the terminal. Thechannel serial numbers shall be followed by
24、001 to 999, with automatic transfer from 999 to 001 at the end of thenumbering cycle.At each retransmission, a new channel serial number shall be inserted immediately after the start-of-messagesignal. The channel serial numbers shall appear in the identification line of the message in the opposite o
25、rder to the onein which the message was transmitted.The length of the identification line must not exceed 69 printed characters. Where necessary, the penultimatechannel serial number of the identification line shall be erased and replaced by a new one; the last channel serialnumber of the identifica
26、tion line shall always be retained, because it also serves as the identification group of themessage.The identification line shall be followed by the routing line.4 Fascicle II.4 - Rec. F.352.2 Routing lineThe routing line comprises:2.2.1 Priority indicatorThe priority indicator, preceded by at leas
27、t one “line change” order, consists of two letters and indicates thefollowing four priorities: QS means that the message is very urgent QU means that the message is urgent QN means that the message is normal QD means that the message can wait.Systems should be capable of identifying these four prior
28、ities at reception, but can deal with only two prioritiesat transmission, confusing QS with QU and QN with QD. A message containing no mention of priority or containing amention other than the ones listed above shall be regarded as a normal message and shall be marked with the code QNat output.The p
29、riority indicator shall be followed by the routing indicator.2.2.2 Routing indicatorThe routing indicator shall be composed of an alphanumerical group of three to seven characters agreed uponby the Administrations concerned. The signs “” (dash) and “/” (oblique) are also admitted.A message may compr
30、ise up to 32 routing indicators distributed over one or more lines, each of which candesignate one or more addressees. The message delivered to the addressee shall contain only the indicator which relatesto him.The routine line is followed by the origin line.2.3 Origin lineThe origin line is precede
31、d by at least one “change of line“ order, followed by the full stop sign (.). The originline comprises:2.3.1 Origin indicatorThe origin indicator is composed in accordance with the criteria set out in the first paragraph of 2.2.2. Thespace between the full stop and the origin indicator is optional.T
32、he origin indicator may be followed by references.2.3.2 ReferencesThese references are optional and may be provided either by the sender or by the system of origin. They shallhave no effect on the processing of the message.The length of the origin line must not exceed one printed line of 69 characte
33、rs.The origin line shall be followed by the text.2.4 TextPreceded by at least one “change of line” order.The format of the text is subject to no special criteria. With regard to the content, the “start-of-message” (SOM)and “end-of-message” (EOM) signals and specific signs or combinations not authori
34、zed by a given mode of operation(cf. the relevant sections) shall not be used.The text is followed by the end-of-message signal (EOM).Fascicle II.4 - Rec. F.35 52.5 End-of-message signal (EOM)This signal, preceded by at least one “change of line” order, is normally composed of the sequence ofcombina
35、tions No. 14, 14, 14, 14 of International Telegraph Alphabet No. 2 (NNNN or ,). This signal may, however,vary according to the mode of operation used.2.6 The format to be used to prepare a service message is the same as that stipulated for an ordinary message (see 2.1 to 2.5).Comments and orders may
36、 be expressed in the abbreviated form described below.An example of such a message is given in 5.2.3 Mode of operation on asynchronous point-to-point circuits3.1 Start of messageGroup ZCZC or + : + : indicates the start of the message (SOM).3.2 End of messageGroup NNNN or , indicates the end of the
37、message (EOM).3.3 Sequence of function signsThe combination of function signs ( ) does not affect the analysis and treatment of the message.3.4 Routing of trafficMessages are routed on circuits and systems in accordance with the arrangements and modalities agreed uponbetween the Administrations conc
38、erned.When two systems are connected by several circuits, the traffic shall be distributed over each usable circuit, ifpossible.3.5 Repetition of messagesMessages shall be repeated only at the request of the partner. There are two kinds of repetition:3.5.1 Repetitions in the form of service notices
39、(retrievals)These are generally used to repeat messages already completely transmitted. The channel serial number of theoriginal transmission must appear in the service notice.3.5.2 Repetitions in the same form as the first transmission (rerun, put-back)Messages shall be repeated in exactly the same
40、 form as the original transmission, i.e. in the same order, with thesame identification and the serial number and via the same circuit.3.6 Specific rules for transmission3.6.1 Interruption of transmissionAfter restoration of the situation, the interrupted message should, as a rule, be repeated with
41、the same serialnumber.6 Fascicle II.4 - Rec. F.353.6.2 Cancellation of a message in the course of transmissionAny message that has begun may be cancelled by transmitting:ANUL NNNNThe channel serial number shall be reassigned to the following message.The cancelled message shall be neither processed n
42、or transmitted, but shall be kept in the archives.3.6.3 Special signsTransmission of characters D, F, G and H in the form of figures and of combination No. 32 is subject to prioragreement.3.6.4 TolerancesNo tolerance shall be admitted for the transmission of messages,3.7 Specific rules for reception
43、3.7.1 Irregularities at receptiona) Absence of start-of-message criterionThe system memorizes the signs received until it recognizes an end-of-message (EOM) sequence or untilan irregularity c), d) or e) below appears.b) Absence of end-of-message (EOM) criterionThis causes the message to be rejected.
44、c) PauseA pause may be defined as a period during the reception of a message in the course of which no data signalis received. If the pause lasts longer than 30 seconds, the system rejects the message.d) Repetition of signsRepetition of signs in excess of the tolerances given in 1.3 causes the messa
45、ge to be rejected.e) Interruption of circuitAn interruption is equivalent to a lapse of reception time of at least one character. Appropriate measuresshall be taken to avoid loss of messages.Note Rejection of the message is held to mean the sending of a notice to the transmitting station or, whereap
46、plicable, its routing to a forward transfer position (see 1.11. 1).3.7.2 Special signsThe presence of characters F, G and H in the form of figures and of combination No. 32 shall not affectreception availability.As far as possible, the presence of characters D in figure case shall be admitted under
47、the same conditions.3.7.3 TolerancesAny tolerances that might be admitted at reception must not be liable to cause the loss, mutilation or duplicationof messages.4 Switched network mode of operation (telex)The rules applicable to the establishment of calls, transmission of messages and disconnection
48、 of calls shall bethose set out in Recommendation F.60.Fascicle II.4 - Rec. F.35 74.1 Start of messageGroup ZCZC or + : + : indicates the start of the message (SOM).4.2 End of messageGroup NNNN or , indicates the end of the message.4.3 Cancellation of a message during transmissionAny message that ha
49、s begun may be cancelled by transmitting:ANUL NNNNThe two answerback codes must then be released and the channel serial number must be reassigned to thefollowing message.The cancelled message shall not be processed or retransmitted, but shall be kept in the archives.5 Examples of formats5.1 Format of ordinary messageZCZC PMS036 (Note 1)QN STOUDHF (Note 2).MARSBRD 77/11 REF 132 (Note 3)TEXTNNNNNote 1 Identification line comprising the start-of-message (SOM) signal and one channel serial number.Note 2 Routing line comprising the prio
