1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 (b) that in various countries possessing public telex networks there also exist numerous private teleprinternetworks using their own exchanges and conforming with the national regulations of the country concerned;(c) that the owners of these private netwo
2、rks are frequently substantial users of the telex service employingmultiple subscriber lines;(d) that, consequently, it is very desirable to allow the through-connection of calls between teleprintersconnected to private exchanges and those connected to the public telex network;(e) that in the teleph
3、one service the ability to establish calls between stations connected to private and publicexchanges has long been available;(f) that the operation of the international public telex service must be neither hampered nor limited by privateexchanges and hence the conditions for interconnection of the t
4、wo types of network should be standardized,declares the following1 Any terminal in a private network that may be directly connected (circuit switched) to a terminal in theinternational telex network must conform to the relevant requirements for terminals in the telex network as laid downin the Serie
5、s F and S Recommendations.2 A private network must not be allowed to provide communication between two external telex stations. For theprovisions concerning interconnection between international leased circuits and the telex network, seeRecommendation D.1 1.3 Where a private network uses a message s
6、tore-and-forward system, it may be authorized to accept and delivermessages from and to the public network. The signals from the private network must always conform with the telexnetworks signalling standards.4 When a private network connected to the telex network offers an external caller the facil
7、ity of selecting a givenextension directly, this should be clearly indicated in the public telex directory.5 Either two-stage or single stage selection may be used as a means of automatic selection of a subsidiary stationin the private network by an external caller.6 For two-stage selection the foll
8、owing provisions should be applied:1) The first stage of the selection should designate the called private network, using a conventional nationalsubscriber number. Following the normal telex procedure, this sequence should start the selection process,resulting in the callers being connected to a tel
9、eprinter (or any other appropriate device in the privatenetwork) that is ready to record a message. For networks where the called telex subscribers answer-back istripped automatically, this answer-back code must designate and be common to the whole of the privatenetwork concerned.2) Application of t
10、he second stage by the calling telex subscriber is optional. The selection sequence used todesignate a particular extension station may have a special composition for the network that is quiteindependent of the national telex numbering scheme, but it must always consist of teleprinter characters.2 F
11、ascicle II.4 - Rec. F.713) If the caller wishes to use the second stage of selection, he advises the private network by sending thesequence XVXV (combination 24, 22, 24 and 22 successively), to which the network responds with aproceed-to-select signal GA (combinations 27, 28, 29, 7, 1 and 31 success
12、ively).4) This optional second stage of selection is ignored by the telex network. The corresponding selection time inthe private network is charged in the same way as a telex call. The composition of the answer-back codestransmitted, where appropriate, after the second stage of selection may theref
13、ore be left to the discretion ofthe subscriber.7 Where single-stage selection is used for connection to extension stations, the following provisions should beapplied.1) The single sequence used to select an extension station must be in the form of a national subscribernumber, comprising a number to
14、designate the called private network followed by further digits to specifythe particular station required. When the caller sends this full sequence of digits, through-connection to therequired extension is achieved, first by selection in the public network then in the private network. Fornetworks wh
15、ere the called telex subscribers answer-back is automatically tripped, the answer-back sentwhen the complete connection has been set up is specific to the selected extension.2) If the caller wishes to communicate, not with any specific subsidiary extension, but with a teleprinter (orany other approp
16、riate device in the private network) that is ready to record a message, the selectionsequence should consist of the number designating the private network followed by the figure 0.3) If the caller only sends a selection sequence specifying the private network (i.e. neither 0, nor a specificextension
17、 number nor an end-of-selection signal is added), the call should be automatically diverted after aperiod of 10 s to a main station.4) If the caller specifies a particular extension station that is engaged or otherwise unavailable, the call shouldbe automatically diverted to a main station.5) With s
18、ingle-stage selection, the answer-back codes for all stations, including extension stations, mustcomply with the requirements in Recommendation F.60 for the composition of telex answer-back codes.8 In the event that the external caller fails either partially or totally to meet the requirements of th
19、e procedures ofa private teleprinter network as in 3 to 7 above, the call should be intercepted by, or directed to, an enquiryteleprinter (or any other appropriate device) in the private network. On no account must the call be terminated by theprivate network if the procedures are not followed.Reference1 CCITT Recommendation General principles for the lease of international (continental and intercontinental)private leased telecommunication circuits, Rec. D.1.
