GB544276A - Improvements in or relating to devices for coin apparatus for telephone plants - Google Patents

Abstract

544,276. Automatic exchange systems. MOE, K.O. May 7,1940, No. 8218. Convention date, May 13, 1939. [Class 40 (iv)] In a prepayment station, cashing in and cashing out take place when the calling party hangs up under control of a polarized magnet or a pair of such magnets energized by the ordinary feed current via contact springs actuated by the coin. As shown in Fig. 2, the magnets I, II are polarized by rectifiers. The insertion of the coin removes a shunt at 9, 10 from the dial springs N and talking instrument T, and shunts the bell at 9, 8 and at 6, 7 prepares a circuit for the magnets I, II which are short-circuited at this stage. When the subscriber hangs up, one of these is actuated according to the direction of current flow in the line, i.e: according as the call has been successful or unsuccessful. The subscriber cannot escape payment by breaking the loop with the dial because the impulse springs are bridged by a rectifier which is in its low impedance condition for the reversed direction of line current. In a similar circuit, Fig. 4 (not shown), an additional hook switch contact enables the coin-operated springs to be simplified. In a modification, Fig.' 3 (not shown), the coin removes a shunt in the form of a rectifier from the talking instruments. This shunt is ineffective for incoming calls because the line current is in the opposite direction. Magnet I may be omitted, cashing in being controlled by the cradle. In a further modification, Fig. 5 (not shown), the line is not fed with current until a coin has been inserted, such insertion connecting a local ground to one leg of the line. In another arrangement, Fig. 6, the magnets are operated over a local ground and one or other leg instead of over the loop. One leg is grounded by the dial off-normal springs b to prevent release by the dial. In the arrangement shown in Fig. 7, one of the magnets controls a contact F which short-circuits the dial N and talking instruments until a coin has been inserted. The magnets are then short-circuited until the instrument is replaced.