Patent GB-191327533-A (GB)
Title: Improvements in or relating to Telephone Systems.
Filed: 1913-11-29
Granted: 1915-04-15
Abstract: 27,533. Automatic Telephone Manufacturing Co., and Newforth, F. Nov. 29. Automatic exchange systems; metering systems.- Metering is effected by a momentary current sent back by the connector through the calling subscriber's test circuit at the moment when the call is answered. When the connexion involves a two-wire trunk the connector serves merely to reverse the current in the trunk when the call is answered, and the metering-current in the test-circuit is originated at a relay-set at the outgoing end of the trunk. The meter magnet, having once responded, is kept energized by the normal current in the test circuit, so that accidental further energizations of the meter are prevented. Specifications 26,301/06, 1419/10, 15,133/11, and 13.974/12 are referred to. Line and master switch. The line switch C, which connects the calling subscriber to a preselected idle connector trunk 109, 110, is of the type described in Specification 1419/10, but has a separate slow-release line relay 22. The masterswitch D, which keeps all the idle line-switches opposite the terminals of an idle connector trunk, is the same as in Spec.fication 15,072/12. Connector. As soon as the connector I is seized, the line relay 68 energizes the release relay 160, which connects ground G<12> to the incoming release wire 129<a> to energize the holding-winding 12 of the line-switch C. The meter magnet 77, in parallel with the winding 12, does not receive enough current to become energized. The numerical interruptions in the calling line operate the vertical and rotary magnets 60, 61 in the usual way to select the wanted line, and, if this line is idle, the side-switch moves to its third position and the ringing-relay 70 is intermittently energized. A slow-release relay 168 in series with the side-switch magnet 66 holds open the circuit of the wipers 57, 59 until the called subscriber's cut-off armature 176 has had time to operate. Metering. When the called subscriber replies to the call, the back-bridge relays 68<a>, 69 are energized. The relay 68<a> reverses the current in the calling line, and the relay 69 closes a circuit through the relays 76, 202 in series. The relay 76 cuts the battery B<1> in series with the battery B in the circuit 129<a>, to operate the meter 77, and is immediately afterwards short - circuited by the self-locking ringing-cut-off relay 202. By this arrangement the metering-impulse is only of short duration, depending on the slow-release nature of the relay 76, and cannot be repeated, for instance, by the called subscriber moving his switch hook. The meter moreover is so adjusted that its armature, when once it has been attracted, is held up by the normal current in the circuit 129<a>, which revents any possibility of a second actuation. Signalling attendant when a disconnected subscriber is called. The connector terminals of disconnected subscribers are wired to the signal-set shown in Fig. 3. When a call arrives at this set, a relay 210 is energized and lights a lamp 209, but the resistance of the relay 210 is too great for the back-bridge relays 68<a>, 69 to become energized. The movement of the enquiry attendant's speaking-. key K momentarily energizes a relay 225, which sends an impulse over one side of the line to energize the relay 69. The ringing-cut-off relay 202 is thus energized, but not the metering-relay 76, which is short-circuited by a back contact of the relay 68<a>. The key K also energizes a relay 218 which open-circuits the lamp 209 and cuts an impedance 221 in circuit with the relay 210. Metering over two-wire junction lines. In one arrangement, the outgoing end of the junction line is provided with a repeater, similar to that described in Specification 15,133/11, but with the addition of two relays functioning in the same way as the relays 76, 202, Fig. 2. In the arrangement shown in Fig. 5, which does not involve a repeater, the relays 300, 305 are energized as soon as the trunk 109, 110 is seized, but the relay 315 is adjusted so as not to respond until both windings are energized by current in the same direction, which is not the case until the current in the junction line 301, 302 is reversed by the response of the called subscriber. The relay 315 then momentarily energizes the metering-relay 308, and short-circuits its own line-winding 314, remaining energized by the local-circuit winding 313.