Patent GB-602927-A (GB)
Title: Improvements in or relating to station identification in electric communication systems
IPC: H04M15/08
Filed: 1946-02-11
Abstract: 602,927. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd., BRAY, F. H., BROOKS, L. J., HARTLEY, G. C., and LOWRY, L. P. Feb. 11, 1946, No. 4141. [Class 40 (iv)] In a telecommunication system the identity of a station is determined in part by the identity of the group identification circuit brought into use when a station is to be identified. As shown in Fig. 1, groups of one hundred subscribers' lines each have their metering wires connected via individual rectifiers RC to a group start circuit GSC, sets of five such start circuits serving consecutive hundreds groups being associated with a 500-line identification finder SAA and an identification circuit IC. For a 10,000 line exchange, the twenty identification circuits are multipled to a common identification control circuit CCR associated through a control circuit finder CCF with the outgoing repeaters OGR. An identification signal is sent over the metering wire from CCR via the selectors and line switch to the corresponding start circuit, the identity of which determines the thousands and hundreds digits, while the corresponding SAA switch finds the marked line, the complete identity then being signalled via IC to CCR. The invention may be adapted for use with the various types of line circuit in common use. Line switch system with meters normally connected via individual rectifiers to common ground for groups of 100 lines, Fig. 2. The direct ground on the commoned positive poles of the rectifiers is replaced by ground via relays SG and BG. The finder SAA has 7 banks to each of the first five of which the metering wires of 100 subscribers are taken, while banks 6 and 7 are used for marking purposes. The P lead is normally at earth potential and a booster potential of 50 volts positive is used for meter operation. Identification is initiated by applying a small positive potential, below the non-operate potential for the meter, to the P lead, from CCR, this potential serving to hold the H relays and busy the connection. Relay SG pulls up to this potential, but BG operates only if a booster metering signal occurs within the group, so that, in the absence of such a signal, SG brings up STA which marks the first two digits over sta4, 5 and starts the finder SAA. High-speed relays HSA and HSB connected in the test circuit will both operate if a 50-volt metering signal is encountered and SAA will step on until it enounters the metering wire to which the identification potential is applied, whereupon HSA only pulls up and cuts the drive, holding over a contact of a control relay (not shown) which stays up until identification is completed. The tens and units digits of the subscriber's number are indicated by the position of SAA via the banks 6 and 7 in a well-known manner. Line finder system with meters grounded over make contacts of cut-off relays, Fig. 3. In this case, extra rectifiers are used to decouple each line, their positive poles being commoned in groups of 100 and wired to a telegraph type relay such as ST. A small positive potential is used to initiate identification as before and the biassing arrangements of ST are such that it operates to this potential, while if a booster potential is encountered, the current flow in the second winding results in the relay being retained on its back contact. Relay ST brings up STA which starts SAA as before, HS pulling up to the identification potential to cut the drive and bring up CG to complete the marking over banks 6, 7. Line switch system, with meters grounded over make contacts of cut-off relays, Fig. 4 (not shown). This arrangement is identical with that of Fig. 3 except in the method of hunting and tripping SAA, modification being necessary to prevent operation of HS to line switches testing on the subscriber's multiple. The small positive potential is fed from the control circuit over a wiper and bank of a control circuit finder and operates ST and STA as described above, but the SAA wiper is grounded over two high-speed relays which both operate to a booster potential so that SAA continues hunting until HSA only pulls up to the identification potential. Uniselector system with meters connected in parallel with cut-off relays to battery, booster operated and holding to earth after metering, Fig. 5. In this case, a positive potential other than the metering potential cannot be applied to the P wire without danger of meter operation, due to the very low non-operate voltage of the meters. The metering wires are commoned in groups of 100 as in Fig. 3, and the common point is grounded over a telegraph relay such as SG in parallel with a condenser, and is also connected via a rectifier RGP to relay BG. Identification is initiated by feeding an A.C. frequency of 500 c.p.s. from a transformer in the control circuit, the grounded secondary of which busies the connection and holds the selectors. The positive half-cycles operate SG, the condenser acting as a reservoir condenser, but BG is unoperated, the positive potential connected to its winding preventing operation except to high positive voltage such as a booster signal. The operation of SG brings up STA and CB (in the control circuit) which replaces the A.C. signal by a small negative potential and starts SAA hunting. The test circuit includes two high-speed relays HSA, HSB designed so that they will both operate if either earth or 50 volts positive is encountered, but HSA only will operate to the marked line, cut the drive and bring up CG. As CG locks HSA and HSB in series, it also opens the circuit of SAA. Specification 602,928 is referred to.