Patent GB-744122-A (GB)
Title: Improvements in or relating to telecommunication systems
Inventor: MERCER RICHARD
IPC: H04Q3/00
Filed: 1950-05-31
Abstract: 744,122. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. May 29, 1951 [May 31, 1950], No. 13535/50. Class 40 (4). Sets of relays or triggered valves are used as line finders or as combined line finders and final selectors, cyclically generated impulses being used for marking and for operating switches as described in Specifications 652,881 and 665,129. Leads marked 1B, 2B ... AB and 1E, 2E ... AE, are connected to battery and earth respectively at instants 1, 2 ... A of a cycle. References for operating and holding leads include the letters OL, HL. In Fig. 1, lines 1, 2 . . . A have access through line finders P and Q to selectors PS and QS. When a call is made on line 1, line relay L1 is followed at instant 1 of the cycle by P1, CO1 with their lower windings in series. They lock to leads HE, HLP. The calling line is extended by P and relay PL operates to seize selector PS. The cut-off relay CO1 is operated through its upper winding when an incoming call is made to line 1. The leads 1B, 2B ... AB, 1E, 2E ... AE, may be interchanged, all the battery leads then being connected continuously to battery (Fig. 2, not shown). In finders P, Q, X, Fig. 3, suitable only for outgoing traffic through selectors PS, QS, XS, there are no line and cut-off relays. When a call is made on line 1, finder relay P1 and selector relay PR operate in series and P1 locks to PR. Selector line relay PL follows and locks PR. Subsequent calls from other lines are taken by finders Q and X as selector relays PR and QR operate. In a modification, Fig. 4 suitable for traffic in either direction, relays P1, Q1 in two finders both operate in series with PR when a call is made on line 1. The line is extended as before to selector line relay PL. With selector PS busy, a subsequent call on, say, line A, operates QR, QA and the line is extended to selector line relay QL. In the last selector, relay XR, when operated, may connect a busy tone generator to indicate, in response to a further call, that all finders are busy. Test lead TL is grounded for a call in the other direction and P1 operates alone, Q1 being short-circuited. A two-stage finder (Figs. 5, 5A, 5B, not shown) is substantially equivalent to two of the finders shown in Fig. 1 connected in tandem. The outgoing lines SLP of the first stage finders P, Q become the incoming lines for the second stage finder. The non-numerical stages of a system like that described in Specification 744,121 are shown schematically in Figs. 6, 7, 8. The lines are arranged in groups 11-1A, 21-2A, A1-AA with line equipments L11-L1A &c. They have access through first and second stage finders P1, Q1 &c. and Pp, Pq &c. and through battery and busy-tone feed equipments PpBF, PqBF &c. to numerical switches NS and to impulse responders IRa, IRb &c. through finders IRFa, IRFb &c. A line 11 seizes the first free finder in a chain P1, Q1, X1 and the relay P11 corresponding to the line operates. The first stage finders P1, P2 ... PA are all connected to second stage finders Pp, Pq ... Px, relays Pp<1>-PpA being allotted to lines with the ten digit 1-A. Each line 11 ... AA has access over each of the inlets or routes Pp, Pq ... Xx to the impulse responder finders IRFa, IRF6, IRFn. The first selectors P1, P2 ... PA may be used as final selectors, in which case they are controlled by third digit selectors Xp3D, Pp3D, Qp3D over operating lead OLFF. A detailed embodiment of this arrangement (Figs. 9, 10, 11, not shown) is substantially the same as that described in Specification 744,121 and involve the busy marking of switches by cyclic pulses. Reference has been directed by the Comptroller to Specifccation 665,129.