Patent GB-191301299-A (GB)
Title: Improvements in Selecting Devices for Telephone and other Exchanges.
Filed: 1913-01-16
Granted: 1913-12-04
Abstract: 1299. Siemens Bros. & Co., and Pettigrew, T. Jan. 16. Exchange systems. - In systems in which a selector has bank contacts divided into groups in the same row, means are provided for restarting the selector, after it has come to rest on a contact of one group, and causing it to hunt until it finds a contact in another group. The invention is particularly applicable for trunk exchanges in which a calling line is automatically connected to an idle record operator, who can transfer the calling line to an idle enquiry operator, who in turn can re-transfer the line to an idle record operator, if desired. In the system shown, the record line a, b from an ordinary exchange terminates at the trunk exchange in a pre-selector VWI, which selects an idle second pre-selector VWII, the bank contacts of which are divided into groups, the upper ones leading to record operators RE, and the lower ones to enquiry operators EN. In the Figure, the relay contacts are not shown in graphic relation to their corresponding windings, but are identified by their reference letters, the relay P, for example, controlling the contacts p<1>, p<2>, p<3>. Connexion to idle record operator RE. When the first pre-selector VWI finds an idle second pre-selector VWII, its test relay Tx energizes in series with a relay P, which closes the circuit of the rotary magnet D<2>, thereby rotating the wipers 4, 5, 6, 7 until an idle record operator is found, whereupon the test relay Ty is energized over switch Q<2>, contact 3, key RK<r>, wiper 6, relay Ty, wiper 7, and contacts of relays P, E, S. The relay Ty locks up over contact ty<1> and its low-resistance winding 2, cuts off the rotary magnet D<2> at contact ty<2>, and closes the circuit of a relay C, which in turn energizes a self-locking relay E, a slow-release relay V, and connects the leads a', b' to the wipers 4, 5. During the connexion with the record operator, the relays P, Ty, C, E, V all remain energized. Transfer of calling line to idle enquiry operator EN. If the record operator wishes to transfer the call to an enquiry operator, she depresses her key TK<r>, thereby opening at contact 3 the circuit of the test relay Ty, and connecting the battery over the switch Q<2> to the wiper 4. The relay Ty opens the circuit of the relay C, which in turn opens the circuit of the slow-release relay V. During the moment following the relapse of relay C and before the relapse of relay V, the relay S is energized over the wiper 4, locks up over its second winding 9, and disconnects the relay E. As soon as the relay V has fully de-energized, the magnet D<2> is again energized over the normal contacts of the relays Ty, E, V, and rotates the wipers. Owing to the relay S being energized, the circuit of the test relay Ty is under the control of the lower set of contacts in the path of the wiper 7, so that the wipers rotate till an idle enquiry operator is found, whereupon the relay Ty is energized, and cuts off the magnet D<2>. The relays C, E, V are also energized as before. The enquiry operator can re-transfer the calling line to the record operator by depressing the key TK<e> when similar circuit changes are effected as when the key TK<r> was pressed, except that the relay F is energized instead of the relay S, so that the circuit of relay E is opened at contact f<1> instead of contact S<2>, and the contact S<3> remains in its normal position so that when the wipers are again rotated they hunt for a disengaged record line. Release of calling line. Either operator can release the connexion by depressing her key RK<e> or RK<r>, thus interrupting the circuit of the test relay Ty without closing that of either of the relays F, S.