ITU-T F 68-1993 ESTABLISHMENT OF THE AUTOMATIC INTERCONTINENTAL TELEX NETWORK《自动洲际用户电报网的建立》.pdf

1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 they have been derived to large extent from the definitions submitted bytelephone experts for studying the analogous problem in intercontinental telephone operation and adapted to the specialfeatures of the telex and gentex services.Preliminary note The w

2、ord continent is not necessarily used in its geographical sense: traffic characteristicsmay cause countries of geographically different continents to be included in one continent (within the meaning of thesedefinitions).1.1 Circuits1.1.1 A national circuit is one connecting two exchanges in the same

3、 country.1.1.2 An international circuit is one connecting two exchanges in different countries, whether or not they are indifferent continents.1.1.3 A continental circuit is one established between two exchanges in the same continent.1.1.4 An intercontinental circuit is one connecting two exchanges

4、situated in different countries in differentcontinents.1.1.5 An intercontinental transit circuit is an intercontinental circuit used primarily for routing intercontinentaltransit traffic.1.2 Exchanges1.2.1 A national exchange is the termination centre for national circuits only.1.2.2 An internationa

5、l exchange is a centre where international circuits, and in general national circuits, terminate.1.2.3 A continental exchange is an international centre where the international circuits terminating there are solelycontinental circuits.1.2.4 intercontinental transit exchange: An exchange of this type

6、 would be directly connected to intercontinentaltransit circuits and would provide facilities to interconnect intercontinental transit circuits and trunks to terminalexchanges. It would also provide facilities for the interconnection of intercontinental transit circuits.1.2.5 terminal international

7、exchange: An international exchange of this type would not be connected directly tointercontinental transit circuits, but would gain access to the intercontinental transit network through one (or more)intercontinental transit exchanges.1.3 Connections1.3.1 international connection: Any connection be

8、tween two stations situated in different countries, whetherestablished between different continents or one continent.1.3.2 continental connection: Connection established between stations within the same continent.1.3.3 intercontinental connection: Connection established between two different contine

9、nts.2 Fascicle II.4 - Rec. F.681.4 Numbering1.4.1 subscribers national telex number: Set of figures to be selected by a caller in the same country to obtain thissubscriber.1.4.2 local number: In national telex networks, when abridged call numbers are used for local or short-distancetraffic, the abri

10、dged number is called the local number.1.4.3 prefix giving access to the long-distance automatic telex network: In national telex networks, whenabridged call numbers are used for local or short-distance traffic, an access prefix should be selected to give access tothe higher level network (long-dist

11、ance level).1.4.4 prefix giving access to the international automatic telex network: This expression is taken to mean the digitor digits that a subscriber must select (if necessary after the prefix giving access to the automatic long-distance telexnetwork) to obtain access to the automatic telegraph

12、 switching equipment for international telex traffic.1.4.5 prefix giving access to the intercontinental automatic transit telex network: This expression is taken tomean the digit or digits that a subscriber must select (if necessary after the prefix giving access to the international telexnetwork) t

13、o obtain access to automatic telegraph switching equipment for intercontinental transit telex traffic.1.4.6 The origin country is free to use only a common access prefix to the international network instead of twodifferent prefixes for access to the international network and the intercontinental net

14、work.1.4.7 telex network identification code: Letter or group of two letters serving to identify the subscribers or stationsof a country (or a network in a country).1.4.8 telex destination code: A group of digits characterizing, for routing purposes, the subscribers or stations of acountry, or of a

15、network in a country.1.5 Routing1.5.1 automatic alternative routing: A facility whereby a call, which cannot find a free circuit on the primary routeat an international outgoing exchange, is automatically diverted to a secondary route.1.5.2 emergency routes: The circuit(s) to be used in case of comp

16、lete interruption or major breakdown of theprimary and secondary routes. The emergency routes may pass through any country.1.5.3 primary routes: The circuits normally used in a given relation.1.5.4 rerouting: When congestion occurs at an intermediate transit exchange, rerouting permits a call to be

17、remadevia a secondary route from the outgoing international exchange.1.5.5 secondary routes: The circuits to be used when the primary routes are congested. The secondary route(s) maypass through the same countries as the primary routes or through different countries. In manual and semi-automaticoper

18、ation, secondary routes may also be used when the transmission on the primary route is not sufficiently good, or iftraffic is to be handled outside the normal hours of service on the primary routes.2 Recommendation for the establishment of the automatic intercontinental telex networkThe CCITT,consid

19、ering(a) that intercontinental telex traffic is rapidly growing; in particular, the development of automatic subscriberselection in intercontinental relations has been made possible. The time differences between terminal countries in suchrelations and the consequent differences in the hours of peak

20、traffic loading may take it economical to employ tandemtransit routing to a much greater extent than has been necessary in the European network. The development of acomprehensive plan for the economical employment of tandem routing depends among other considerations, onagreement on numbering and rou

21、ting plans;(b) that a worldwide service includes countries that are served by several telex networks. A telex subscriberscall number in a worldwide service must contain all the digits to be transmitted by the caller in order to establish theconnection, irrespective of the routing channel;Fascicle II

22、.4 - Rec. F.68 3(c) that to facilitate automatic routing and charging for calls, the number of digits to be examined by thecharging equipment must be limited;unanimously declares the following:2.1 General characteristics of the network2.1.1 It must be possible to establish the intercontinental netwo

23、rk by means of:a) submarine or underground cable telegraph circuits;b) telegraph circuits via telecommunication satellites; andc) telegraph circuits on radio channels.2.1.2 When circuits via various transmission facilities exist between two intercontinental transit exchanges, all suchcircuits must,

24、for automatic selection purposes, be regarded as included in a single system.2.1.3 Administrations will agree on whether a given group of circuits should be operated on a one-way, bothway orpartially divided basis.2.1.4 The traffic to be routed over these circuits may be either telex or gentex traff

25、ic; it may be either transit orterminal traffic.2.1.5 Countries (or networks) should be connected by direct circuits where this can be justified taking into accountthe relative economics of transit switching and bothway working where the time difference between the terminalcentres makes this a signi

26、ficant factor.2.1.6 Where it is not practicable to provide direct circuits, the number of transit exchanges involved in a normallyrouted call should be reduced in so far as possible.2.1.7 Where the same group of circuits carries traffic originated by subscribers in the country providing facilities a

27、ndtransit traffic originated by another country, the Administration providing the transit exchange shall ensure that thetransit calls receive a grade of service not inferior to that given to their own subscribers.2.2 Identification of telex subscribers2.2.1 For international purposes, a subscribers

28、national number should be accompanied by one or two letters, calledthe telex network identification code, characterizing either:a) the subscribers country, if in that country there is only one telex network; orb) the telex network to which the subscriber belongs in a country where there are several

29、networks operatedby different agencies.2.2.2 An identification code is especially valuable for countries possessing several telex networks operated bydifferent companies and when national numbers do not clearly distinguish between such networks. In suchcircumstances, it is recommended that the ident

30、ification code should be clearly published in national directories.Furthermore, Administrations shall ask subscribers to give every possible publicity to their telex identification letters(by including them in the letterheads of their correspondence for example).2.2.3 The answerback codes for subscr

31、iber equipment used in intercontinental telex services should include the telexnetwork identification code allocated to the country or network concerned (see Recommendation F.60, 3.4.2).2.2.4 For Administrations using two-character telex network identification codes these codes should be the same as

32、the identification codes of their country (or network) for the telegram retransmission system (see RecommendationsF.31 and F.96).2.2.5 The one-character telex network identification code X is used to identify mobile stations that may be connectedto the international telex network, regardless of the

33、transmission medium used (maritime mobile-satellite, VHF, HF).The two-character codes commencing with X will not be allocated to national telex networks.2.2.6 The list of telex network identification codes has been compiled by the CCITT and published in accordancewith Recommendation F.96.Note If in

34、any country the telex and gentex networks are separate, two identification codes might benecessary, one for telex and the other for gentex.4 Fascicle II.4 - Rec. F.682.3 Routing2.3.1 On international circuits digits only will be transmitted for selection control.2.3.2 For each country, or for each n

35、etwork in countries possessing several telex networks, a group of two or threedigits the telex destination code will uniformly characterize each country or network for the purposes of selection inintercontinental transit circuits. (See Recommendation F.69 for the list of telex destination codes.)2.3

36、.3 The access prefix to be selected in an outgoing country by a subscriber wanting to put through a call to anothercountry via the intercontinental transit network shall be decided on by the Administration responsible for the callingsubscriber. This is a matter for internal regulation.2.3.4 There ar

37、e two possibilities in relations between the international exchange of the outgoing country and anintercontinental exchange:2.3.4.1 There are direct trunk circuits between the international exchange in the outgoing country and theintercontinental exchange (see Figure 1/F.68). On these circuits, it s

38、hould suffice to transmit the destination code of thecountry required, followed by the national number of the subscriber required;2.3.4.2 There are no such direct trunk circuits (see Figure 2/F.68). There are then direct circuits between theinternational exchange in the outgoing country and the inte

39、rnational continental exchange in the transit country,adjacent to the intercontinental exchange. Hence this adjacent exchange will have to be traversed to reach theintercontinental network.2.3.5 Code 00 should be used as the standard access prefix for traversing a continental exchange. A country tha

40、tmight experience difficulty in accepting this 00 code may choose another code for traversing its continental exchange,subject to a bilateral agreement with the other Administration concerned.Fascicle II.4 - Rec. F.68 52.4 Automatic alternative routing2.4.1 Provision must be made for the possibility

41、 of using automatic alternative routing (see Figure 3/F.68). Theputting into operation of automatic alternative routing is a question of the network situation, as it will often bepreferable to create new telegraph circuits on a congested route rather than to bring automatic alternative routing intos

42、ervice. Be it noted that the automatic alternative routing method should be considered only if the peak hours on CDare different from those on CF and FD; otherwise, it is to be feared that transit switching equipment F will becomesaturated.2.5 Automatic re-routing2.5.1 The complications resulting fr

43、om automatic re-routing would be out of all proportion to the benefits to beexpected therefrom.2.6 Call recording2.6.1 In principle the originating exchange is responsible for timing calls, booking calls, repeated attempts, etc. Theresponsibility of an intercontinental transit exchange should be lim

44、ited to providing a connection between the callingexchange or subscriber and the required exchange or subscriber.2.6.2 In accordance with Recommendation U.23, the elapsed time is normally taken as the basis for fixing thechargeable duration even where calls are routed over HF radio circuits fitted w

45、ith ARQ equipment on the first orsubsequent links in the connection.2.7 Grade of service2.7.1 Refer to Recommendation F.64.2.8 Use of radiotelegraph circuits with ARQ equipment2.8.1 Fully automatic operation on a radiotelegraph circuit incorporating ARQ equipment can be considered only ifthis circui

46、t possesses adequate stability.2.8.2 Before incorporating a circuit with ARQ equipment in the fully automatic switched network, theAdministrations must carry out extended trials.2.8.3 These trials should be made under normal traffic conditions, over a minimum period of three consecutive hourschosen

47、from the busy period (or periods), when heavy traffic is foreseen to occur on the route under consideration(allowing for the traffic, whether terminal or transit, that prevails on the route according to the season).2.8.4 The condition that must be fulfilled before a circuit can be accepted for use i

48、n a fully automatic network is thatits mean efficiency factor measured over periods of 20 consecutive seconds each, shall not fall below 80% for morethan 10% of the total time involved in the measurements. The measurements must be repeated as often as will benecessary for the Administration to have

49、an assessment of the suitability of the circuit.6 Fascicle II.4 - Rec. F.682.8.5 The attention of the Administrations is drawn to the fact that, before offering fully automatic transit working ona radio route incorporating ARQ equipment, the grade of service on the route under consideration must be only one calllost in 50.2.8.6 If these conditions are not complied with, it would be better to retain semi-automatic operation.