Patent GB-451864-A (GB)
Title: Improvements in telephone or like systems and impulse senders for use therein
IPC: H04Q5/00
Filed: 1935-02-12
Abstract: 451,864. Automatic exchange systems; impulse transmitters. POLLAK, J. E., 20, Holborn, London.-(Associated Electric Laboratories, Inc. ; 1033, West Van Buren Street, Chicago, U.S.A.) Feb. 12, 1935, No. 4531. [Class 40 (iv)] The selection of the appropriate meter in the case of an outgoing call from a subscriber on a 10-party line is effected by the transmission of a preliminary digit of eleven impulses, one of which is of a special character and is differently situated in the digit for each subscriber on the line. Impulse transmitter. The dial is constructed with eleven fingerholds and is designed to send up to eleven impulses by the engagement of a rotary cam with spring 16, Fig. 3, in the usual manner. When the dial is set to transmit eleven impulses, a cam 26 on a disc 22, Fig. 6, secured to the hub of the finger-disc shaft, rocks a pivoted member 13 which closes springs 11 and remains set until restored by a further cam 25 at the end of the return movement. A second disc 20, Fig. 4, is secured to disc 22 in any one of ten positions as determined by the engagement of a pin 33 with one of the holes 34, and at a correspondingly-variable point in the impulse transmission closes contacts 18 by means of cam 21 for the duration of one impulse. This closure is however only effective to modify the character of the corresponding outgoing impulse when spring 11 has been first closed, as described in the next paragraph. The construction of dial forms the subject-matter of Specification 451,897. Specifications 226,152 and 234,036, [both in Class 40 (iv)], are referred to. Circuit arrangements, Fig. 1. The calling line is extended to a trunk circuit T at which line relays 102, 103 and release relay 104 operate. At each impulse of the preliminary digit prior to the special impulse, relays 102, 103 release and the impulses are repeated to magnet 134 of switch S1 and to magnet 5 of the meter-selecting switch S. At the special impulse which involves the connection of ground to the a-wire over springs 11, 18 provided that the dial has been set for the digit 11, relay 102 only responds, the switches are not stepped, and relay 105 operates to prevent any further stepping of switch S. The remaining impulses of the digit cause switch S1 to advance to position 10 in which relay 101 is operated to extend the calling line to the first selector. During the further extension of the connection, relays 101, 105, 108 remain operated and release relay 6 of switch S is also energized to maintain wiper 2 in operated position. When the called party replies, booster current over conductor 152 operates the selected meter M1 .. M10. If the calling party omits to dial the meterselecting digit he is unable to extend the connection because the operation of relay 101 is dependent on the receipt of such a digit by switch S1. If he attempts to get the call charged to someone else by simulating the production of a special impulse by attaching extra wires to his instrument, the extra-long special impulse which will probably be transmitted will cause the operation of relay 106 which opens the locking circuit of relay 105 and thus prevents the subsequent operation of 101.