Patent GB-447106-A (GB)
Title: Improvements in telephone systems and pay stations for use therein
IPC: H04M17/02
Filed: 1935-11-29
Abstract: 447,106. Automatic exchange systems. TELEPHON-APPARAT-FABRIK E. ZWEITUSCH & CO., GES., 6, Salzufer, Charlottenburg, Berlin. Nov. 29, 1935, No. 33185. Convention date, Feb. 21. [Class 40 (iv)] In a system wherein the value of the inserted coins at a prepayment substation is registered at the exchange and is checked against the charge for the call as determined by the initial digits of the wanted number, each coin closes a contact to send an impulse of current of a strength dependent on the value of the coin. The impulses control a pair of registering relays connected to one wire with opposing windings in the other wire in series with the line relay, one or both of the relays responding according to the strength of the current. As shown, contacts g10, g50 are closed by coins of different values, e.g. one unit and five unit pieces, and connect earth to the a wire either through resistance Wi or not to operate either relay X10 alone or both relays X10, X50. Relays X10, X50 repeat impulses to switches W10, W50 respectively, so that their settings correspond respectively to the total number of coins inserted and to the number of five unit pieces. When the receiver is removed, line relay A energizes, followed by V1 and the pre-selector VW hunts. At the first dialled impulse, D pulls up and transfers the loop to impulse relay E, which holds V1 and repeats the impulses to the discriminating switch MW. Meanwhile, the operation of D advances the sequence switch ST to position 1, in which an auxiliary switch HW steps in synchronism with the switch W50 until the latter reaches normal. The totalling switch SW then steps, ST being in position 2, until it reaches a position marked by HW. The cross-connections are arranged so that the number of five unit pieces is converted into single units allowing for the fact that the number of these pieces is also recorded on the switch W10. Relay Q energizes, ST advances, and the setting of W10 is transferred first to HW and then to the totalling switch SW, which is thus set to a position corresponding to the total value of the coins inserted. The sequence switch ST then moves to position 6. Dialling relay V2 connects up R1 at the end of the first impulse train and R2 at the beginning of the second. In the case of toll calls (first digit O), the discriminating switch MW is set by the first and second digits to a position which should correspond to that of SW, and if this is so relay F energizes in parallel with R3 and opens the circuit of TR. If F does not energize, the operation of TR brings about the release of the connection. In the case of local calls (first digit other than O), for which the charge is always the same, the check is made as soon as R2 pulls up. Metering relay M pulls up on reply, and when the calling party hangs up, relay SM energizes over the b wire, connects KM to the a wire and by inserting its highresistance winding releases E. Relay KR operates in a circuit prepared by M, and the coin-collecting magnet KM energizes momentarily in series with P, which disconnects KR. Free calls denoted by the digits OO bring about the operation of relay G which prevents the energization of TR and M. In the case of long distance calls, the insertion of coins is signalled to the operation by means of an auxiliary microphone Mk. To avoid crackling noises, contacts g10, g50 are connected through a choke Dr to the centre of the induction coil In and apply earth first through a condenser K1.