GB602388A - Improvements in electrical impulsing circuits - Google Patents

Abstract

602,388. Impulse correcting circuits. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Oct. 13, 1945, No. 26843. Convention date, Nov. 23, 1944. [Class 40 (iv)] In an impulse correcting circuit the duration of the corrected impulse is determined by the time required for a condenser to be charged or discharged through a resistance until its potential is such as to cause the striking of a gas discharge tube. In the circuit shown, impulses incoming from wires 1, 2 are repeated by relay J to the vertical magnet V of a group selector switch under control of the correction circuit 10, 12, 13. On connection from the preceding switching stage dialling relay C operates immediately to earth on wire 3. Impulsing relay A operates to the incoming loop over wires 1, 2 followed by release relays B and D and by relay G. Relay D connects dial tone to line. Relay B earths wire 3 to hold C and the preceding switch. On impulsing, each release of A operates J which locks at J1, energizes the vertical magnet V and releases G which disconnects the operating circuit for J. On operation, J disconnects the charging circuit for condenser 12 which discharges for a predetermined time through resistance 13 until gas discharge tube 10 fires, whereupon its anode current through the lower winding of J neutralizes the effect of the holding current in the upper winding and J releases, re-operating G, de-energizing the vertical magnet V, restoring the charging circuit for condenser 12 and opening the anode circuit of 10 at J1. Vertical magnet springs V1 at each impulse complete a pre-energizing circuit for A to' assist re-operation when the impulsing loop recloses. On the first vertical step F operates to disconnect dial tone and transfer the circuit of the upper coil of relay C to the back contacts of A. Relay C is now held mainly by pulses over its lower winding by relay J, but partly also by the initial pulse over its upper winding from relay A so that the effective length of the impulse received by it is increased sufficiently to ensure that it does not release during impulsing. At the end of the impulse train C releases and completes a rotary stepping circuit and when an idle outlet is found, E operates over wiper 6 to stop the switch stepping and switching relay H operates in the usual manner, the remainder of the relays, except F, releasing. If all outlets are .busy, 11th step cam springs CS release relay D which opens the rotary stepping circuit and sends out busy tone. The selector releases in the usual manner, F releasing when the switch is normal.