1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$./0%2!4)/. G0G0.5-“%2). G0G02/54).!.$G0G0-/“),%G0G03%26)#%30%#)!,G0G053%3G0G0/(b) that the international telephone service is becoming more and more automatic, and that only
2、a few manualcircuits will be kept to form a reserve network;(c) that it is therefore necessary to provide automatic circuits for special uses other than telephony;(d) that telephone circuits assigned for special uses must, when needed, be made available to the specialservices as rapidly as possible;
3、(e) that it must be guaranteed that, after the circuits have been used for a special purpose, they will be returnedto the telephone service without delay;(f) that the switching of circuits for special purposes should not disturb the operation of telephone service.recommendsthat the following provisi
4、ons be observed:1 In an international telephone relation, the number of automatic circuits assigned for special purposes should bein reasonable proportion to the total number of circuits, so that their occupation will not hamper the flow of automatictelephone traffic.2 Circuits to be used for specia
5、l purposes should be passed at the outgoing and incoming ends through transferpanels on which the wanted circuit is disconnected manually from the telephone equipment and connected to theterminal of the special service concerned.Alternatively, circuits assigned for special uses should be fitted, in
6、the telephone equipment, with a device forautomatic switching to the transfer panel of the special service, the operation being commanded by the latter. (Thismethod is preferable because with the first method a telephone call could be interrupted if proper care is not exercised.)3 The switching oper
7、ations should take place under the control of the outgoing international maintenance centre(IMC). The IMC may delay or limit the provision of telephone circuits for other purposes, particularly whenrestrictions are imposed on the telephone traffic.4 The following arrangements should be followed when
8、 special connections are set up and cleared:a) The occupation of a telephone circuit for a special purpose should be marked on the transfer panel at theoutgoing end; conversely, if such a circuit is in fact engaged, it must be marked busy in the telephoneswitching equipment.b) A circuit assigned to
9、a special use may not be taken for the service in question if a telephone call is inprogress. However, arrangements should be made to ensure that the circuit cannot be engaged by anothertelephone call when the call is over (preliminary blocking).c) The circuits in a group of telephone circuits that
10、are reserved for special uses should be last-choice circuits,to reduce the risk of finding them busy when required.2 Fascicle II.2 - Rec. E.300d) When a circuit is free, the supervisor in charge of the transfer panel at the outgoing end takes the necessarysteps to withdraw the circuit from the telep
11、hone service. The responsible supervisor at the incoming end isthen asked to make the necessary operations if the telephone equipment is not disconnectable by remotecontrol.e) While awaiting notification from the incoming end of completion of transfer to the special service, theoutgoing supervisor t
12、ests the connection before making it available for its new functions.f) The same procedure is followed at the outgoing end when the circuit is restored to the telephone service.To prevent a subsequent telephone call from being ineffective, care must be taken to clear the special call atthe incoming
13、end first.5 Bookings of leased circuits or order lines for programme transmissions are arranged in advance and are noturgent. The delays required by the connection of two circuits in tandem when a connection is operated entirely inautomatic transit give rise to no particular difficulties.6 Where tel
14、egraph systems are concerned, the primary requirement is rapid replacement of the faulty VF bearercircuit. In view of the delay which would occur in employing two separate links to form a reserve circuit, it appearsthat in relations in which automatic transit switching is the normal method of operat
15、ion, a direct circuit should beretained.Such a direct circuit could be manual or automatic. An automatic circuit would normally be used to carry thetelephone traffic. It should be noted that this will then be used as a first-choice route and will thus carry the heaviestload. The risk of finding it b
16、usy, when needed, will therefore be at its maximum.In such circumstances, preliminary blocking of the wanted circuit should be effected (see 4b) above). As longas the equipment is unable to perform this operation it will be preferable to keep one manual direct circuit.7 The delay in establishing pho
17、totelegraph calls via an international phototelegraph position transit centre (transitIPP) is not so critical. In this case, application of Recommendation E.320 will speed up the placing of two circuits endto end at the transit centre to establish the connection, and it will not be necessary to keep
18、 direct circuits in relationswhere automatic switching is the method normally used for telephone calls in transit.8 The same circuit should not be assigned to more than one special service, so that the various transfer panels forsuch services may be placed separate from one another should the terminal country so wish.
