Patent GB-194701-A (GB)
Title: Improvements in or relating to apparatus for counting telephone calls
IPC: H04M15/30
Filed: 1923-03-06
Abstract: 194,701. Ellis, D. S. March 7, 1922, [Convention date]. Mechanical switches; actuating; handles.-In making a telephone call, a subscriber inserts a key in an electromechanical switch 77, Fig. 1, and turns it to the dialling position in which the transmitter is cut out of circuit, and when a reply is received, moves the key to the speaking position and thereby operates a meter embodied in the key. In the case of an ineffective call the key may be turned back and removed. When the capacity of the meter has been reached, the key is no longer effective, and means are provided for preventing operation of the switch by an improper key. On insertion of the key 21 in the switch, projections 117 engage in slots 116 in a barrel 86 on a shaft 94, the latter being moved longitudinally against the action of a spring 96, thereby causing a disc 101 to release spring contacts P which prevent calling other than by the use of the key. The barrel 86 carries cams 88, 89, 90 which co-operate with sets of spring contacts. Turning of the key to the first operative position A closes line contacts whereupon the subscriber's line switch is operated by lifting of the receiver. In the second or dialling position B, contacts are operated which remove a shortcircuit from the impulse-sender and shortcircuit the transmitter and receiver while dialling is taking place. The reversal of current upon the reply of the called subscriber causes shortcircuiting of the transmitter. On turning the key to the third or metering position C, contacts are operated to free the transmitter, and to prevent the setting up of a fresh connection without moving the key. In this position the rectangular end 123 of the shaft 94 registers with the recess in the key containing a plunger 23 so that the latter is moved inwards by the spring 96 to actuate a counter. When the capacity of the meter is reached a projection 71 on the arm 25 engages in a slot 72 in the plunger and so prevents further use of the key. At the end of the conversation the key is turned until it is diametrically opposite to the initial position and removed, the spring 96 allowing of this rotation of the shaft 94. If for any reason, such as the use of a fraudulent key, the contacts P are not returned to normal in the metering position a relay 115 energizes, releasing a lever 108 normally held in an inoperative position. The lever 108 in turn releases a spring 112 which drops and locks the shaft 94 against further movement by the engagement of a pin 102 thereon in a slot 114 in the spring. At the same time the relay 115 operates contacts cutting out the telephone and key. If an attempt is made to use a key in which the plunger has been forced in, contacts 46, 47 closed in the depressed position of the plunger cause a thermostat 45 to function in the dialling position of the key, rendering it useless. To indicate to the subscriber the various positions of the key the barrel 86 has a number of recesses 132 which coact with a spring-pressed stud 135 to give an audible click as each is reached.