Patent GB-381818-A (GB)
Title: Improvements in or relating to telephone installations employing a plurality of exchanges
IPC: H04Q3/62
Filed: 1932-02-17
Abstract: 381,818. Automatic exchange systems. MIX & GENEST AKT.-GES., 5, Geneststrasse, Sch÷neberg, Berlin. Feb. 17, 1932, No. 4745. Convention date, Feb. 18, 1931. [Class 40 (iv).] A private branch exchange is provided with means by which an incoming call may be transferred from one subscriber to another, a local enquiry connection being first established to the second wanted subscriber. The incoming call is set up by the operator over the connector AW, which for outgoing calls acts as a line finder. When the call is to be transferred, the enquiry connection is established automatically over the line finder SW and connector LW employed for local calls, and, on the first called subscriber hanging up, the switch AW advances again to complete the fresh connection, the line of the wanted subscriber being marked by the connector LW. Incoming call to subscriber N1. Line relay AR energizes and closes a circuit for the calling lamp AL and relay HR, which, through relay VI (1), lights the busy lamp BL. The operator connects her set to the junction by actuating the keys Sa, Sb, thus disconnecting the lamp AL, and operates her dial (not shown) to control the magnet Da of the switch AW. Relay P1 (III) energizes over contact vx of a relay operated momentarily at the end of the impulsing and locks, while relay P2 is connected to the test wiper c and energizes in series with the wanted subscriber's cut-off relay T1. The key Sa is restored, and relay U1 energizes over the junction and connects up relay K which applies ringing current from a source RQ. Upon reply, feed relay A energizes followed by relay A1, which lights the supervisory lamp CL. The key Sb is restored and relays U1, K fall back, completing the talking circuit. Transferring call to subscriber N9. T'he subscriber N1 actuates the key Tal, thus operating the differential relay X over one winding. Relay V2 energizes and connects up relay U, which locks and connects the righthand winding of the repeating coil Ue to the enquiry trunk ar, br, relay U1 being again bridged across the junction to hold the connection. Line relay Rr energizes and causes the finder SW to rotate into engagement with the trunk ar, br, whereupon relays V, Tr energize in the usual manner to extend the connection to the connector LW. Line relay A2 energizes and dialled impulses are repeated thereto by relay A to set the connector. If the subscriber N9 is idle, switching relay P pulls up and ringing takes place, and upon reply, relay 7 responds and the enquiry connection is completed. The subscriber N1 now hangs up, causing relays A, A2 to fall back, whereupon a circuit is closed over wire dr for relays U3, U2. The former holds relay V and marks the line of the subscriber N9 by applying ground through relay C to wire d9, while the latter connects wiper d of the switch AW to test relay P3 instead of to test relay P1, which is used when an outgoing call is being set up. Relay A1 falls back and disconnects relays P1 (III), P2, T1, while the magnet Da re-operates to step the switch AW into engagement with the line of the subscriber N9, whereupon relay P3 pulls up in series with relay C and again connects up relays P1 (III), P2, the latter energizing in series with cut-off relay T9. Relay C disconnects relay P and the switches SW, LW restore to normal. The differential relay X now energizes in series with feed relay A since one winding is short-circuited by relay U2, and releases relay U to complete the fresh connection. Relay U2 falls back after an interval, whereupon relay X releases and disconnects relay U1 from the junction. Release is controlled by a relay Z (not shown). If for any reason the enquiry connection is not obtained, the subscriber hangs up, and the relapse of relays A, A1 relights the calling lamp AL, while relay P2 falls back and completes a circuit for the magnet Da for restoring the switch AW. Outgoing call. The calling line is connected over the finder SW to the connector LW which in response to a digit indicating an outgoing call effects the operation over wiper c of a relay which grounds wire an. A self-interrupting circuit is thereby closed for the magnet Da for stepping the switch AW into engagement with the calling line, which is marked by battery over wipers d of the switches SW, LW. Test relay P1 therefore energizes, followed by relay P2 which extends the call to the junction. The operation of relay C releases the switches SW, LW. Specification 139,000, [Class 40 (iv), Telephones &c.], is referred to.