Patent GB-1237379-A (GB)
Title: Improvements in or relating to automatic telephone systems
Inventor: CURTIS GERALD
IPC: H04Q3/00
Filed: 1967-10-23
Abstract: 1,237,379. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. 23 Oct., 1968 [23 Oct., 1967], No. 48131/67. Heading H4K. In an exchange system in which a subscriber is normally connected over a single path through a switching network to an outgoing junction, an alternative path to this junction via a special relay set is set up if the subscriber requires a special service. The latter includes centralized operator controlled services of which overseas phonogram" is given as an example. Such services are demanded by three digit IXX dialled codes and special translation facilities are provided for dealing with them. The system utilizes self-steering cross-bar switches of the type described in Specifications 739,905, 890,235 and 983,507. General description.-The exchange is a group switching centre having attached thereto: local subscribers who gain access to the router R (i.e. group selector) via a distributer (not shown) and local transmission relay groups LTRG; dependent exchanges which gain access via incoming relay groups ITRGA; and U.A.X.'s which gain access via relay sets ITRGB. The relay groups ITRGA have facilities for reconstituting the first digit, since this is lost in gaining access, and for transmitting it together with the succeeding digits to a free register in the group IRA. The relay sets ITRGB are connectible to register/senders in the group IRSB (first digit reconstruction in this case being effected at the originating UAX) and the local relay sets LTRG have access to their own register/sender group LRS. Received digits are passed to a router control RC where they are discriminated and a local LCDR or STD coder (i.e. translators) seized accordingly. The coder reverts routing and alternative routing data, metering rate and the number of digits to-be-expected after the prefix code to the control RC. Thereafter RC controls, by selfsteering techniques, the connection of the calling incoming relay set to a local trunk TT (DSA), outgoing-to-trunk-transit-network trunk MFJ or outgoing-to-dependent (or other GSC) exchange trunk OGJ. V.F. signalling is used on the MFJ trunks and V.F. or loop disconnect signalling on the OGJ trunks. Special service call.-Irrespective of how such a call originates, the special IXX code is eventually received in the router control RC and this then applies to local coder LCDR for a preliminary translation. The latter consists in the address of one or more special relay sets COTRG and it is used by the control RC in order to set up a connection from the calling incoming relay set, the A and B stages of the router and a special trunk CO to the indicated set COTRG. The 1 +X code in RC is passed to COTRG which provides a 6-digit translation thereof. RC is released during the setting up of a connection to COTRG but is reseized thereafter in order to pass the code portion of the 6-digit translation to an STD coder STDCDR. The latter supplies instructions to RC which enable it, with the aid of junction marker JMKR, to connect COTRG to a suitable MFJ trunk. STDCDR also instructs COTRG to seize a free V.F. sender MFSDR so that routing digits can be sent into the trunk transit network in order to gain access to the required special operator service. Reference has been directed by the Comptroller to Specification 1,101,725.