Patent GB-241932-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-10-22
Abstract: 241,932. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Richardson, R. G., and Bellamy, J. I.). Oct, 23, 1924, [Convention date]. Automatic exchange party-line systems; metering.-In a party-line system having a, separate meter at. the exchange for each station on a partyline, a meter-selecting device at the exchangein testing the calling line to ascertain which station thereon is calling, sets itself in a position corresponding to the order of the calling station en the line, and determines the actuation of the proper meter on the reply of the called party. The invention is described as applied to a system including a number of party-lines each having thereon four stations A - - D. Each station is provided with a polarized relay P, - - P4 one end of the winding of which is earthed over a switch-hook contact when the receiver is removed : the relays P1, P2 at stations A, B are negatively and positively polarized respectively, and the other ends of their windings are connected to the upper talking conductor, whilst relays P3, P, at stations C, D are also negatively and positively polarized but are connected to the lower talking conductor. On the initiation of a call, a meter-selecting switch MSS, associated with the engaged trunk circuit TC, is advanced under the control of a stepping switch X common to the exchange, and applies negative and' positive high potential battery in succession first to the upper and then to the lower talking con ductor. When the potential particular to the calling station is applied, the polarized relay P1 - - P4 thereat responds, and by removing a shunt from a resistance r1 - - r4 in its circuit, causes the switch MSS to be arrested. Each group of, say, 100 party-lines has at the exchange four multi-contact relays 501 - - 504, the contacts of the relay 501 being connected to the meters such as MI of the stations first in order on the party lines, those of the relay 502 to the meters such as M2 of the second stations on the partylines, and so on. All the meters such as M1 - - M4 of a party-line are connected to a common meter conductor at the line switch LS. When the called party answers, a switch Y common to the exchange is stepped round, and on arriving at a contact corresponding to the position of the switch MSS, earths the metering conductor over the wiper 12 of this switch, and energizes a multi-contact relay 501 - - 504 corresponding to the order of the calling station on the party-line. The energized relay 501 - - 504 completes a circuit for the proper meter M1 - - M4. Metering is prevented and an alarm actuated if two parties on the same line call simultaneously or close upon one another, or if a party attempts to prevent metering by vibrating his switch-hook. Metering party-line calls. Assuming first the subscriber A, Fig. 1, on the party-line removes his receiver to make a call, the line switch LS operates in known manner and extends the calling line to an idle trunk circuit TC, energizing a line relay 120 which locks up and grounds the starting wire 43 of the common stepping switch X over an interrupter 523. This switch advances on the relapse of its stepping magnet, and its contacts are so connected that as it slips round, the conductors 41, 42 are alternately grounded. The operation of the switch X, however, does not affect the trunk circuit TC until the wiper 521 has engaged the pick-up contact 524 and the stepping magnet is again energized, on which the conductor 44 is earthed over armature 522 and wiper 521, and a pick-up relay 110 is energized. The relay 110 locks up and transfers both talking wires to the meter-selecting switch MSS, which operates in the following manner to identify the calling subscriber on the party-line. The stepping magnet of the switch X relapses and advances the wiper 521 on to the first contact 525, and upon energizing again earths the conductor 42, thereby closing a circuit for the stepping magnet 125 of the switch MSS, the wipers 10, 11, 12 of which engages their first contacts. A negative high potential from the battery 17 is now connected over wipers 11, 10 to the upper talking wire 1, and a test circuit is closed over armature E1, impulse contacts and contacts i1 of the impulse transmitter at the calling station A, and switchhook contacts h1, for the polarized relay PI. which responds and inserts the resistance from the above circuit. At the next step, the switch X transfers earth from the wire 42 to the wire 41, preparing a circuit for a stop relay 150 and opening the circuit of the stepping magnet 125, which on falling back inserts the relays 130, 140 in the above-described test circuit between the wipers 10, 11. The relay 130 energizes, but due to the presence of the resistance r1, the marginal relay 140 remains inert. A circuit is thereby completed for the stop relay 150, which locks up, unlocks relays 120, 110 to disconnect the switch X and stop the switch MSS, and switches the calling line through to a group selector. If the subscriber B had been the calling party, the connection of the negative high potential battery 17 to the line wire 1 in the first position of the switch MSS would have had no effect upon the positive polarized relay P2. The resistance r2 remains shunted in the test circuit, and on the relapse of the stepping magnet 125, both relays 130, 140 respond, the latter relay holding open the circuit of the stop relay 150 and permitting the switch MSS to advance to its second position in which positive high potential battery 16 is applied to the upper wire 1. The polarized relay P2 thereupon responds, removes the shunt from resistance r2, and when the test relays 130, 140 are inserted, cause the relay 130 only to energize and arrest the switch MSS in its second position. If the subscriber C calls, the connection of positive or negative high potentials to the upper talking wire in the first and second positions of the switch MSS, has no effect upon the negative polarized relay P3 which is connected at this time to the lower talking wire 2. In position 3 of the switch MSS, however, high negative potential battery 17 is connected to the lower conductor 2, the polarized relay P3 responds, and the switch is arrested as before in its third position. Similarly, if the subscriber D calls, the positive polar. ized relay P4 does not respond until positive high potential is connected to the lower conductor in the fourth position of the switch MSS. After receiving the usual dialling tone, the calling party dials the wanted number, and on the reply of the called party, the reversal of current over the conductors 101, 102, causes the response of a polarized relay 190, the upper winding of which is connected in parallel with a resistance 196 in the conductor 101. Relay 190 locks over its lower winding, shunts the resistance 196 to improve the talking circuit, shunts a resistance 197 provided to prevent premature operation of relay 190, and earths the starting wire 50 of the common switch Y. The switch Y advances its wiper 511 on the back-stroke of the stepping magnet, and after it arrives on a pick-up contact 514 or 516, earth is applied to the pick-up wire 49, energizing relay 180, which places a further shunt across resistance 196, disconnects the left end of resistance 197, and connects the metering wire 107 through relay 170 to the wiper 12 of the metering switch MSS. As the switch Y successively earths its contacts, the multi-contact relays 501 - - 504 are energized and successively connect battery to all the first, second, third, &c. meters of the group of party lines with which they are associated. Only the meter M1 - - M4 of the calling subscriber on the calling party line is, however, energized, since at the moment that the metering wire 107 is earthed over wiper 12 of the switch MSS and wiper 511 of the switch Y, only that multi-contact relay is energized appropriate to the order of the calling subscriber on the party line. The relay 170 energizes in the metering circuit and unlocks relay 190, which disconnects the start and pick-up wires 50, 49 and opens the metering circuit. On the release of the connection the relay 150 relapses and closes a circuit for the release magnet 126 of the switch MSS. Simultaneous calls. If two subscribers on the same party-line call simultaneously, or if a second subscriber calls before the switch MSS has completed its operation, neither call is metered and an attendant's alarm is actuated. Since in these circumstances the test circuit for the relays 130, 140 at any time includes a path to ground at one of the calling sub-stations which does not include a resistance r1, r2, &c., both these relays pull up during the test in positions 1 to 4 of the switch MSS, so that the stop relay 150 is not energized, and the switch moves to its fifth position. In this position the test circuit extends from the grounded resistance 68 connected to the fifth contact, over wiper 10, relays 130, 140, wiper 11, and relay 160: the marginal relay 140 remains inert, the stop relay 150 is energized, and owing to the energization of relay 160 a circuit is closed over an alarm wire. AL. If one of the calling subscribers obtains connection with a line, when the called party answers, relay 170 is energized over resistance 172 instead of over the metering wire, and the trunk circuit is disassociated from the switch Y as previously described. Fraudulent operation. If a subscriber attempts to prevent metering by vibrating his switch-hook while the switch MSS is operating, and thereby disconnects ground at his switch-hook at the instant that the testing circuit over his polarized relay P1, P2 &c. is completed, neither of the relays 130, 140 respond, the stop relay 150 is preventing from operating, and the switch MSS moves to its fifth position, causing the closure of the alarm circuit AL as described in the previous paragraph. Sp