Patent GB-175163-A (GB)
Abstract: 175,163. Automatic Telephone Manufacturing Co., Ltd., Gillings, C., and Nercer, R. Dec. 29, 1920. Automatic exchange systems; metering systems.-Auxiliary apparatus is provided for effecting a variable charge according to the exchanges between which a connection is made. In the arrangement shown in Figs. 2 and 3, all the exchanges in a given area axe given distinctive numbers, which have no relation to the dialling numbers of the subscribers whom they serve, and as soon as s connection has been completed, impulses corresponding to the number of the final exchange are sent back from a. machine 44, 45, 46 at the exchange to operate a switch Q at the originating exchange, which collects the appropriate number of metering impulses from a machine 60. 61, 62, &c. Switches similar to Q are associated with the outgoing ends of all the interexchange trunks in the area. A connection is represented as having been extended through a repeater E, which has been seized over a particular level of the first group selectors at the originating exchange, over an inter-exchange trunk 21, 22, a selector F and repeater G at a second exchange, an inter-exchange trunk 23, 24, and a selector K and connector H at a third exchange. A relay 35, energized as soon as the connection is completed, closes a circuit through a resistance 39 and a relay 37, which becomes partially energized and pulls up its armature 40. At the next operation of the starting cam 44 of the constantly-running impulse machine 44, 45, 46, relay 37 becomes fully energized and pulls up its other armatures, locking itself so as to be independent of relay 35 and connecting the impulse springs 49 to the lower incoming talking wire. If the final exchange is No. 17, 17 impulses are now transmitted by the springs 49 to operate the magnet 50, which moves the switch S to its 17th position and repeats the impulses at contact 53 to magnet 54, which moves the switch Q to its 17th position. The magnet 54 also repeats the impulses at contact 59, but this is without effect as the repeater E is at the originating exchange. The springs 68 then close the circuit of relay 70, which locks itself up and cuts out relay 37 so that further cycles of impulses from the springs 49 will be ineffective. When the wanted subscriber answers the call, the bach-bridge relay 32 reverses the current in the trunk 23, 24 to energize an electropolarized relay 31, which energizes relay 33 to reverse the current in the trunk 21, 22, thus energizing the electropolarized relay 30, which energizes the reversing relay 34 and closes a circuit through a resistance 73 and relay 72. The relay 72 becomes partially energized, pulling up its armature 74, so that at the next closure of the starting circuit 75 by the common impulse machine 60 - - 65 the relay becomes fully energized and connects the release wire 81 through the switch arm 55 to one of the impulse circuits 95. 66. 59, 67, which transmit respectively 1, 2, 3 and 4 impulses per cycle. In the present instance the switch Q is in its 17th position corresponding to exchange No. 17, which may be assumed to be at such a distance from the originating exchange as to require a charge of three units, and the 17th contact 57 of the switch arm 55 is therefore connected to the wire 59. Three boosting impulses now pass over the circuit 59, 55, 77, 82, 81 to operate. the meter, and the stopping circuit 94 is then closed to energize magnet 80, which releases the switch Q. The switch S operates in a similar manner, but since in the present instance it is not at the originating exchange it is ineffective for metering, because the release wire corresponding to 81 terminates at the selector F. The above-described arrangements do not provide for metering calls internal to a single exchange, since such calls do not involve a repeater E. For this purpose the connectors at each exchange are associated with a machine 106, 117, 115 which delivers a single booster impulse over the release wire when a call is answered. The operation of this machine is similar to that of the machines already described, and it need onlv be pointed out that the cut-off relay 119 has a double locking circuit so as not to be de-energized until both subscribers have disconnected themselves. If the system is such that the destination exchange is completely determined by the first set of impulses repeated by the repeater E, the switch Q may be set by these impulses instead of by impulses re-transmitted from the final exchange. In this modified arrangement it is unnecessary to denote the different exchanges by arbitrary numbers. Specifications 122,747 and 172.995 are referred to, the latter in the Provisional Specification only.