Patent GB-158276-A (GB)
Abstract: 158,276. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Wicks, J.). Jan, 19, 1920, [Convention date]. Automatic exchange systems and apparatus; coin-freed systemns and apparatus.-In a measured service system, a substation provided with a charge-assessing apparatus may establish a privileged connection without the insertion of a coin, but when connection with a non-privileged subscriber is attempted, unless a coin is deposited the completion of the connection is prevented. According to the system described, a substation A is connected to a first selector E through a line switch C and repeater D. Special second selectors as F<1>, accessible from a certain level in the first selectors, have access to groups of trunks extending to privileged positions, such as the operators' equipment O, whilst other levels in the selector E are accessible to the usual second selectors as F and connectors as H, which complete connection to ordinary subscribers in the usual manner. If no coin is deposited and connection is attempted with a non-privileged subscriber A<1>, when connection has been extended to the second selector F, a shunt is placed across the impulse-repeating armature 86, and contact of the line relay of the repeater D, and the repeater D is rendered ineffective, but if connection is established with a special second selector F<1> leading to a privileged position, a resistance X<1>, included in the release circuit, causes the response of a relay 55 in the repeater D, which removes the shunt from the armature 86 and its contact. When a coin is first inserted, however, the polarized magnet P of the coin-freed mechanism is connected between one line and earth, thereby unbalancing a differential relay 54 and causing the removal of the shunt. The batteries which effect the operation of the coin-freed mechanism on the subscriber A hanging up are rapidly interrupted to prevent the armature of the magnet P thereof from sticking. Establishment of a privileged connection (no coin required). When a subscriber A removes. his receiver, the line switch C operates in wellknown manner to extend the line to a trunk leading to an idle first selector E. The line relay 57 of the repeater D inserted in the seized trunk is energized, current flowing through both windings of the diffe rential relay 54 and the impedance coil 62. Subsequent response of the slow release relay 58 completes a holding-circuit back to the line switch C from earth through the low-resistance relay 55, which energizes and breaks a shunt across the armature 86 and its contact. A loop is also established across the trunk conductors 101, 103 which includes the upper winding of the polarized relay 59, which does not respond, and the impedance coil 60. The line relay 104 of the first selector E is thereby energized, causing the response of the slow-acting relay 105 which prepares the circuit of the vertical magnet 110 and closes the usual holding circuit extending back to. the preceding switch. This circuit includes a resistance X about equal to that of the relay 55, which therefore remains energized. The first series of impulse now sent de-energize the line relay 57 and cause corresponding interruptions in. the circuit of the line relay 104 of the selector E, the wipers of which are stepped-up to the level in which are terminated the trunks to the special second selectors, and then rotated to find an idle trunk in well-known manner. The line relay 200 of a secod selector F<1> is now energized and a holding circuit established from earth G<5> over the resistance X<1>, which fulfils the same function as resistance X. The second series of impulses are repeated as before by the line relay 57, the shaft of the switch F<1> is raised to the desired level, and an idle trunk leading to the wanted operator's position O is seized in the usual manner. The energization of the line relay 250 causes the response of the slow-acting relay 251, which establishes the usual holding circuit over the resistance X<2>, and lights the supervisory lamp L. Release is effected as in general practice by hanging up the receiver at the calling station A. Prevention of a non-privileged connection if coin is not deposited. Operation is the same as previously described with the exception that the trunk conductors 101, 103 are extended to a second selector F of the general trunking system. The holding circuit from ground G' includes no resistance X, with the result that the low resistance relay 55 is short-circuited, and relapsing, completes a shunt across the armature 86 and its contact, thereby rendering the repeater ineffective to extend the connection further. Establishment of a non-privileged connection; refund or collection of coin. When a coin is inserted before calling, the line is extended to a first selector E as previously described, but earth is connected to the line 22 through the high resistance of the polarized magnet P, thereby unbalancing the differential relay 54 which responds and completes a circuit through the relay 56. The latter locks up over the armature 83, earths a holding-circuit through the low-resistance, relay 55, and breaks the shunt circuit across the armature 86 and its contact at the armature 84. The calling subscriber now operates his impulsesender, and the switches E, F. H extend the connection in well-known manner to the wanted subscriber A'. If the wanted subscriber is busy, on the calling subscriber hanging up, the line relay 57 is de-energized, thereby energizing the slow-release relay 61, and on the relapse of slowacting relay 58 completing a circuit for the slowrelease relay 50, which earths the test wiper 36 at the armature 64, and opens both sides of the line at the armatures 63, 65. The armature 65 also connects the battery B<1>, over relay 51 and line 22, to the polarized magnet P, which operates to refund the coin and restore the coin-freed mechanism, and disconnect itself from the line 22. On the response of the relay 51 the interrupter magnet 97 operates to break the circuit through the polarized magnet P intermittently and prevent its armature from sticking. Both line conductors are also earthed through a condenser over armatures 68, 69. When the circuit is broken by the disconnection of the magnet P at the calling station, the de-energization of relay 51 is followed by the relapse of relay 50 and the release of the line switch C on the removal of earth from the wiper 36. If the subscriber A<1> is free, on removing his receiver, current through the loop across the conductors 101, 103 is reversed and the response of the polarized relay 59 is followed by the energization of the relays 53 and 52. Relay 53 locks up and connects the incoming line conductors direct to the trunk conductors 101, 103, the line relay 300 of the connector H now being maintained energized over a complete metallic circuit including the calling subscriber's line. As long as the line circuit is closed at the calling station, the marginally adjusted high-resistance relay 100 does not energize, but when the subscriber A hangs up at the end of the conversation, it responds and breaks the locking- circuit of the relay 53, which opens the circuit of the line relay 300 of the connector H at the armature 76, 79, and initiates the usual releasing operation of the switches H, F, E. The relapse of the relay 53 causes the energization of the slow-acting relay 50, when the same operation of the coin-freed mechanism occurs as previously described, except that since the relay 52 is energized the battery B<2> is connected to the polarized magnet P, which is now actuated to collect the coin. The line switch C is released as previously described.