Patent GB-264932-A (GB)
Title: Improvements relating to prepayment arrangements for automatic telephone systems
IPC: H04M17/02
Filed: 1925-10-29
Abstract: 264,932. Siemens Bros. & Co., Ltd., and Caswell, A. E. Oct. 29, 1925. Impulse transmitters for automatic exchange systems. Calls for which coins must be deposited are allotted a number or numbers of digits different from those allotted to calls for which no charge is made, and the substation impulse transmitter is provided with means for counting the number of digits dialled and, if this number denotes a chargeable call, for preventing the completion of the call if the requisite coins have not been deposited. For example, free calls to enquiry operators, fire stations, &c. may be made by dialling one, two or three digits whilst calls to ordinary subscribers have at least four digits. In this case the dialling of a fourth digit completes a circuit for short-circuiting the microphone and releases a sliding member which tests for the presence of the requisite coins. If these are not present, the sliding member shortcircuits the impulsing contacts so that the fourth and further digits are ineffective. If, on the other hand, the coins have been correctly deposited, selection proceeds as usual but the shortcircuit across the microphone must be removed by cashing-in the coins before conversation can proceed. In the apparatus shown, three coins must be deposited for each chargeable call and jamming of these in the shoot is prevented by providing a separate support for each, the insertion of the support for any coin other than the first being controlled by the presence of a coin immediately below. The impulse transmitter 2 is fitted with a toothed wheel 3 which at each setting of the dial effects through a rider 4, a pivoted rocker 7, and a pawl 9, the movement of a ratchet wheel 6 through one step. If the dial is set for a fourth digit, a cam 13 on the ratchet shaft rocks a lever 14 which completes at contacts 15 a short-circuit for the microphone and releases a spring-controlled sliding member 50 to test for the presence of coins. The coins are inserted into a shoot formed by two grooved members 16, 17, and upon insertion a coin rests first upon a projection on a spring-controlled plate 37. A lever 47 is then depressed causing a bar 44 to rock about its pivot 43 and to move with it towards the shoot the plate 37 and three other coin-supporting plates 19 - - 21. A crossbar 30 causes a pivoted catch 29 to look the plate 19 across the shoot but the plates 20, 21 are withdrawn when lever 74 restores so that the first coin drops on to the bottom plate 19. When lever 47 is depressed after the insertion of the second coin, the presence of the first coin on plate 19 causes catch 33 to lock plate 20 so that the second coin falls on to the second plate. The third coin similarly comes to rest on plate 21. If the three coins have thus been deposited, the testing member 50 on release engages the third coin and is unable to move appreciably. When the call is completely established and the wanted partly replies, the depression of cashing- in button 57 causes a pivoted piece 58 to lift the locking-bar 32 so freeing the plates 19 - - 21 which are withdrawn from the shoot and the coins drop into the till. The member 50 is now able to move across the shoot thereby opening contacts 56 tu remove the short-circuit from the microphone. When the subscriber hangs up his receiver, bar 32 is raised to a greater extent than before, causing a shoulder 67 to restore member 50 and a further shoulder 59 to operate lever 11<a> which effects the release of ratchet wheel 6. If the call has been unsuccessful, a member 64 operated by hanging up the receiver will direct the coins into the return shoot 65. If the coins have not been deposited when the fourth digit is dialled, member 50 closes contacts 54 which short-circuit the impulse contacts. If coins have been unnecessarily deposited for a free call, spring arm 14<c> of member 14 is not positioned between button 57 and pivoted member 58 so that even if the button is pressed the bar 32 is not lifted and the coins are not collected but will be returned at the end of the conversation. The lever 47 may be eliminated by causing each coin on insertion to effect the rocking of the bar 44.