Patent GB-142265-A (GB)
Abstract: 142,265. Relay Automatic Telephone Co., Bygrave, L. C., and Inman, T. M. April 7, 1919. Automatic exchange systems.-Subscribers are arranged in large groups, such as 1000, incoming calls to each group being effected by a complex switching-organization comprising three or more sets of intermediate lines. The invention is described with reference to a system in which switching is effected entirely by relays. Fig. 1 shows the arrangement of trunks for the incoming calls to a group of 1000 subscribers forming part of an exchange of 10,000. An X at the intersection of two lines represents the possibility of a connexion. Each group of incoming lines A, B, &c. has access to a corresponding group A1, B1, &c. of first intermediate lines, any line in group A being connectible to any line in group A1 &c. Each first intermediate line has access to one line in each of the groups A2, B2, &c. of second intermediate lines. Each group of second intermediate lines A2, B2, &c. has access to a corresponding group A3, B3, &c. of third intermediate lines, any line in group A2 being connectible to any line in group A3 &c. The 1000 subscribers are divided into sub-groups, one of which is shown at S12345, and each of these sub-groups is served by one or more lateral lines A4, A5, B4, &c. from each group of third intermediate lines. It will be seen that there are a large number of alternative routes from a given incoming line to a given subscriber, and of these a route must be pre-selected of which no segment is already engaged; for example, if subscriber S1 is wanted, and lines A4, A5 are already occupied, it is useless to attempt a connexion over the groups of lines A2, A3, althrough there may be idle lines in these groups. Fig. 2 shows the third or test circuits of those trunks which are represented in Fig. 1 by con. tinuous lines. The calling-line is extended to the wanted thousands section of the exchange as described in Specifications 29615/13, 6210/14, and 9840/14, and the numerical impulses are received by a common impulse-responding device, as described in Specification 16619/14, which energizes a relay f individual to the sub-group to which the wanted subscriber S1 belongs, and connects battery to a circuit 3 individual to the subscriber S1. In describing the operations by which a connexion is set up, it will be assumed that all the lines are idle to begin with. The relays c1, e2, &c. of all lines of the group A1 are energized in a circuit 1, and a circuit 5 then energizes a chain of relays j1, k1, m2, n1, g1 corresponding to a particular route of connexion. At the same time, circuits are closed for other chains of relays, such as j2, k2, m2, n1, g1, or jl, k1, m3, n2, g2, or j1, k4, m5, n3, g3, corresponding to alternative routes, but these circuits are immediately opened bv the relays k1, g1. One of these alternative chains would, however, have been energized if any part of the first route has been already occupied. The relay j1 energizes relay j2 over a circuit 4 individual to the line A over which the call arrives; relays j1, k1 energize relay o1 over a circuit 6; rolays k1, m2 energize relay p1 over circuit 7; relay g1 energizes relay h1 over circuit 3. The relays j2, o1, p1, h1 are the connecting-relays which complete the connexion from the calling- line to the wanted subscriber S1. These relays close a locking-circuit 8 through their own windings and through relays q1, r1, t2, n1, u1, v1. The relays q1 de-energizes relays e1, j1, so that the occupied first intermediate line is unavailable for further calls: relay r1 opens the circuit of relay k1, so that the occupied second intermediate line is rendered unavailable, the next call energizing the relay k2 and not k1; relay t2 opens the circuit of relay m2, so that the occupied third intermediate line is rendered unavailable; relay u1 opens the circuit. of relay g1, so that the next call energizes relay g2 instead of g1; relay v1 is the called-subscriber's cut-off relay. Specification 105,363 also is referred to.