Patent GB-197711-A (GB)
Title: Improvements relating to prepayment devices for telephone systems
IPC: H04M17/02
Filed: 1921-12-22
Abstract: 197,711. Siemens Bros. & Co., Ltd., Collyer, J. E., and Barker, R. Dec. 22, 1921. Hiring telephones; coin action, mechanicalconnection, thrust, and multiple-coin; coin-slit closing-devices.-In a prepayment device for telephone systems in which a coin receiver is moved by an operating lever to discharge coins, during which time it co-operates with contacts for preventing fraudulent use, four contacts are provided, I to send characteristic signals to the exchange according to the coins inserted in the case of trunk calls, II to open the subscriber's loop in the case of local calls if three pennies have not been inserted, III to short-circuit the transmitter and shunt the receiver until the contact II has been operated, and IV to short-circuit the dial contact when the coin-receiver has been turned a short distance. Dialling is done with the operating lever d in the normal position, coins are then inserted, and the lever depressed for speaking. The shaft of the coin-receiver or drum b is secured to the shaft c<1>, Fig. 7, of the lever d through a spring, but is locked until the lever reaches the lower position by the engagement of a finger f<1> with a cog-wheel e<6>, whereupon a detent f<5> integral with the finger f<1> drops into a recess d<2> in a disc d' on the shaft c<1>, and the drum b is then rotated by the tensioned spring, the motion being controlled by a governor e in mesh with the cog-wheel e<6> which is driven by a pawl secured to the drum. The lever is locked in the lower position by the engagement of the detent f<5> with the end of the recess d<2> until the movement of the drum is completed, whereupon a pin f<6> strikes a. finger f' swinging the members f<1>, f<5> to release the lever d and lock the cog-wheel e<6>. A shutter g, Figs. 9 and 12, moves with the operating lever, closing the coin slots and retaining the coins in the drum until the movement is complete. The parts are returned to normal by raising of the lever. Each coin slot in the drum b contains a pusher i, Fig. 9, sliding on a pair of pins i<1> and moved outwards by the insertion of the coin to bring the tip i<3> into position to contact with a lateral shaft j on a bell-crank lever j<3> carrying at the other end a, roller j<4> in engagement with the contact spring I. The pushers are spaced radially, and the tips are formed to give a characteristic signal for each coin. The contact II is controlled by a bell-crank lever m<2>, Figs. 6 and 12, which tends to enter a slot n<2> in a lateral shaft n, but is prevented by the engagement of a roller k thereon with a disc k<2> forming part of the drum b until a recess k<1> comes opposite the roller. Levels m<1> engage in slots n<1> in the shaft n, the slots being stepped laterally, with. regard to the levers, so that a spring n<x> causes a longitudinal movement of the shaft in a series of steps upon retraction of the levers by engagement with the pusher tips i<3>. If three pennies have been inserted, the shaft n makes three steps, and the bell-crank lever m<2> is engaged by a cam n<3> before the roller k falls into the recess k<1>, preventing the operation of the contact II to open the subscriber's loop and release the connection. In the case of a manual exchange, the closing of the contact II lights a supervisory lamp. The shaft n is returned to normal by the engagement of a projection n<4> in a cam-groove n<5> in the drum b. The contacts III and IV are operated by bell-crank levers m<5> which engage cam discs k<3>, k<4> The operation of the contacts during the turning of.the drum is shown by the gaps in the horizontal lines of Fig. 4.