Patent GB-284811-A (GB)
Title: Improvements in or relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1926-11-26
Abstract: 284,811. Siemens Bros. &. Co., Ltd., Long, D. P., and Peters, C. L. Nov. 26, 1926. Automatic and semi-automatic exchange systems; metering.-In a system employing a pair of relays S, Z, Fig. 2, associated with a mechanical timing device to control metering, the reply of the called party causes these relays to perform a cycle which results in the energization of a meter-preparing relay M, and upon release the relays perform a second cycle which completes the metering circuit. If the calling line in a local connection is seized for a preferred trunk call, metering is prevented by a differential relay Z, Fig. 2, in series with the line relay, which becomes unbalanced and energizes, releasing or preventing the operation of the relay M. An extra vertically-moving wiper F is provided in the first selector for selecting the metering cam to be used the meter being operated one, two, or three times according to the level to which the switch is raised. The operator sets up trunk calls over a special first selector (Fig. 5) and the connectors which are used for local connections. The Provisional Specification refers to Specification 222.246. Ordinary call, Figs. 2 and 3. When the first selector (Fig. 2) is seized, line relay A energizes first over the incoming test wire c and then over the loop. Differential relay X is inoperative. Relays V, D energize in the usual way, and relay L energizes at the first impulse and short-circuits relay X. Test relay T is operated to battery when an idle connector is found, and further impulses are then repeated over the b-wire. At the connector (Fig. 3), relay N energizes over the incoming test wire c, while line relay A energizes over the b-wire, and responds to the repeated impulses. The wanted line is tested between the relapse of relavs D. G by relay T. which energizes if it is idle, and ringing takes place in the usual manner. When the called subscriber replies, ring-cut-off relay TR energizes, and disconnects ringing relay S, and answering supervisory relay Y, Fig. 2, pulls up. Relay L falls back, removing the short-circuit from relay X, and relay Y prepares the circuit of relay S, Fig. 2, so that relays S, Z go through a cycle and send an impulse over contacts s4, z3 to energize relay M, which locks and prepares the metering circuit at contact m1. If the wanted line is busy, relay TR energizes as soon as relay G falls back and connects busy tone and flash battery to the a-wire. Relay Y operates intermittently, but Delays S. Z do not perform a cycle. When the subscribers hang up, relays Y, A fall back, but release relay V is held over contacts m4, z4. The circuit of relay S, Fig. 2 is again prepared at contacts a4, m3, and relays S. Z go through a second cycle, completing the metering circuit over contacts s1, z1 to the metering cam selected by wiper F. Relays V, M relapse and initiate release. Preferred call, Figs. 4, 5, and 3. The operator plugs into the jack J of the special first selector (Fig. 5). and moves her key to the left, energizing relay C, which short-circuits its high-resist. ance winding. Line relay A energizes over the sleeve circuit and responds to the interruptions of the dial DL, which is connected up by the energization of relay D, Fig. 4, which also holds relay C. Connection is made with an idle connector (Fig. 3) in the usual manner, and further impulses are repeated over the b-wire. During each train of impulses, relay E is energized at back contact a<2>, and connects battery to the a-wire to operate relay TL, Fig. 3, which locks and substitutes relay TK for relay T to act as the test relay. After relay D, and before relay G falls back. relay TK energizes in a local circuit even though the wanted subscriber may be engaged in a local call. If, however, he is engaged in a trunk call, relay K is short-circuited by direct battery fed over front contacts tk4, l2 of another connector, and in this case relay TIt energizes and sends back a busy signal. The earthed winding 3 of relay TK is connected to the a-wire, and if the wanted subscriber is the calling party in a local connection, differential relay X at the first selector (Fig. 2) is unbalanced and energizes. If metering relay M is already energized, it is released and the prepared metering circuit is opened. If relay M is not energized, it is prevented from doing so. When relay TK switches through, line relay A. Fig. 3, falls back, but ringing relay S is still short-circuited at contact tl4 to prevent ringing. At the first selector (Fig. 5), answering supervisory relay Y responds, and substitutes high-resistance relay S for line relay A in the sleeve circuit, extinguishing lamp SL. Relay A is held over winding 2. The operator informs the subscriber of the waiting trunk call, and asks him to hang up. She then moves her key to the right, unbalancing the bridged differential relay X, Fig. 5, which energizes and connects up ringing current. This energizes relay L, Fig. 3, which locks, marks the line engaged in a trunk call, and disconnects relay TL.