Patent GB-301322-A (GB)
Abstract: 301,322. Telefunken Ges. fiir Drahtlose Telegraphie. Nov. 26, 1927, [Convention date]. Automatic exchange systems.-Two groups A, B of wireless or wired-wireless stations working on different high frequencies are connected over a low-frequency junction L. Substations Ta, Tb may be associated with the junction stations Ao, Bo over low-frequency connections directly or on an automatic exchange. Fig. 3 shows one form of equipment at Ao (Bo being identical) including a modulator-generator Sand de-modulator Em. The station Ta is connected over separate lines for incoming and outgoing calls. The junction L includes, in addition to the talking wires La, Lb, wires w, t, u for the intercontrol of relays Y at Ao and Bo. The apparatus Ao, Bo may be in the same room. Specification 267,151 is referred to. Call from A1 to B. The high-frequency energy arrives over J3 and relays C, U are energized. The first digit (signifying that a. B station is wanted) is repeated at c3 to magnet K which sets a selector k to energize relay P, which locks itself, energizes E (in a local circuit D1) and Y, and bridges the junction through D2. Relay E at e1, e2 starts up S. Relay Y switches the talking circuit from Ta to L and busy tone X from L to Ta, and over the wire t energizes the corresponding relay at Bo (unless there is a local call in progress in the group B, in which case the relay Y at that exchange is disconnected at eb, busy tone comes back, and the call from A can go no further). A second digit (denoting the particular B station that is wanted) is repeated over the junction at c2 to complete the call by controlling relay E (at Bo) which controls S, at e2. Release is effected by the de-energization of relays C. Call from A1 to Ta. In this case a single digit is dialled of such value as to energize relay R instead of P. Relay R locks itself, switches in the incoming line of Ta, and closes the local circuit of E to start S. Call from Ta to A1. The outgoing line of Ta is normally connected to E, which repeats the dialled digit to S at e2. Call from A1 to A2. In any such local call, relays C, U are energized at Ao but not P or R. Then if E is energized by an attempted call from Ta or B a circuit is closed for relay Sp (not shown), which opens sp1 to disable S, so that the attempted call cannot be put through. Modifications. A simpler arrangement is described, Fig. 2 (not shown), in which the stations Ta, Tb are omitted and the relays Y and junction wires w, t, u are dispensed with. In other modifications, separate to and from junctions are provided between A and B, and there may be a single two-way conection between Ao and Ta. A call from an A station to a B station may be made by dialling a single digit, the effect of which is to start a device for transmitting the characteristic calling signal of the wanted station. Alternatively, selecting impulses may be sent out by the return of the selector k to normal. The Specification as open to inspection under Sect. 91 (3) (a) comprises also a circuit arrangement similar to that described above with reference to Fig. 3 but showing details of the control of the relay sp, and a further circuit arrangement, Fig. 2 (Cancelled) (not shown), in which relay E is connected so that it cannot be energized from B if a local call is in progress at A, so that sp is dispensed with. This subject-matter does not appear in the Specification as accepted.