Patent GB-172460-A (GB)
Abstract: 172,460. Automatic Telephone Manufacturing Co., Ltd., (Automatic Electric Co.). Sept. 30, 1920. Automatic exchange systems; metering systems; par@y-line systems.-A separate meter is provided at the exchange for each subscriber on a party line, the operation of the appropriate meter being selectively determined by the circuit connection of the subscriber against whom the charge is to be made. Two methods are described. In the first, which is only suitable for two-party ines, one of the substation circuits is so modified that when the receiver is removed an operating-circuit is momentarily connected to line, the operation of the appropriate meter being determined by the absence or presence of this circuit. According to the second method, in which more than two subscribers may be connected to a party line, a resistance is inserted in the line circuit at the calling substation when the receiver is removed, and remains there during the setting up of the call, the magnitude of this resistance governing the selective operation of a marginal relay switching device at the exchange which prepares the circuit of the appropriate meter. First method. A two-party line 2, 3, Fig. 1, serving subscribers A<1>, A<2>, is connected to a wanted subscriber B over a rotary line switch C and connector H of well known type. The substation circuit at the station A<1> is provided with no special equipment, but that at the station A<2> is provided with an additional contact 25, whereby the line conductor 2 is momentarily grounded when the receiver is removed. Assuming the subscriber A<1> calls, the slow release line relay 6 and the switching relay 5 are simultaneously energized over the line circuit. The relay 6 completes a circuit for the switching relay 4 and the rotary magnet 7 over the lower holding winding of the relay 5, and connects the test wiper 23 to the above circuit at a point between the relay 4 and the rotary magnet 7. The relay 5 prepares the circuit of the appropriate meter-magnets M<1> at its armature 12, whilst the rotary magnet 7 operates in known manner to select a trunk leading to an idle connector H, to which the line is extended on the response of the switching relay 4. The line and release relavs 62, 63 of the connector H are energized in the usual way, a holding circuit being established for the relays 4, 5 over the conductor 33. The connector H is then operated by the dialling impulses to extend connection to the wanted subscriber. During the setting up of the connection the two windings of the differential trunk relay 29 are traversed by currents in oppcsition and the relay 29 remains inoperative, but on the response of the backbridge relay 61 when the called subscriber answers, the current through the right-hand winding of relay 29 is reversed, and the relay responds. The metering magnet M<1> is then energized over the armatures 30, 16, 12, whilst the right-hand winding of the relay 29 is short-circuited to improve the talking circuit. When the subscriber A<2> makes a call, the energization of the switching relay 5 is prevented. Before the switch hook reaches its uppermost position and the line circuit is completed, the line relay 6 is energized over the conductor 2 and contact 25. The upper winding of the switching relay 5 is thereby short-circuited over armatures 9, 10, whilst the lower winding remains short-circuited by the armature 11. The operation proceeds as before, but since the relay 5 remains de-energized, when the called subscriber answers, the meter magnet M<2> is energized. Second method. This modification is described as applied to a system in which a twoparty line may be connected to a waited subscriber over a line switch C, Fig. 2, controlled by a master switch D, and a connector H. If the subscriber A<1> makes a call, on removing his receiver the line relay 6 and the marginal relay 4 are energized over the line, circuit. Relay 6 completes a circuit for the pull-down winding 74 of the line switch, whilst the relay 4 energizes the switching relay 5, which transfers the metering circuit from the magnet M<2> to the magnet M<1>, and locks up over the armature 31 and release trunk conductor 75. A circuit is completed for the magnet M<1> in series with the left-hand winding of the trunk relay 77, but the magnet M<1> does not respond until this winding is connected in parallel with the low resistance right-hand winding, on the response of the differential relay 29, which operates when the called subscriber answers. When the subscriber A<2> calls, the circuit of the relays 4, 6, is completed as before, but the resistance 83 and the winding of a polarized relay 81 are included therein. The resistance of this circuit is such that the marginal relay 4 does not respond, and the switching relay 5 remains inert. On the response of the called subscriber, therefore, the outer magnet M<2> is energized instead of the magnet M<1>. The reversal of current in the calling subscriber's talking circuit also causes the polarized relay 81 to respond, thus short-circuiting the resistance 83 and rendering the talking circuit more effective. Fig. 3 is a diagrammatic representation of the second method applied to a party line with four subscribers D, E, F, G with different resistances in their substation circuits, and three marginal relays 43, 44, 45 in series with the line relay 66, the marginal relays being associated with switching relays 53, 54, 55 which control the circuits of the meter magnets MG, MF, ME. MD. If the subscriber D calls, all the marginal relays respond with the line relay 66, and a circuit is completed for the meter magnet MD, whilst if the subscriber E calls, the resistance included in the line circuit is such that only the relays 43, 44, 66 operate and the magnet ME is energized. Similarly the resistances in the substation circuits at stations F and G are such that when the subscriber F calls, relay 43, 6E respond, and when subscriber G calls, only the line relay 66 operates, the circuit of the appropriate magnet MF or MG thus being completed.