GB1386212A - Integrated circuit for push button pulse dialing - Google Patents

Abstract

1386212 Impulse transmitters ITT INDUSTRIES Inc 4 Jan 1973 [21 Jan 1972] 558/73 Heading H4K An impulse transmitter utilizing MOST integrated circuit technology comprises a plurality of recirculating shift registers into which binary coded representations of digits keyed up on a subscribers keyboard are serially entered in parallel format, a static shift register into which each digit is passed in serial digital pulse train format after decoding from the recirculating shift registers, a clock pulse generator whose output is divided so as to continuously produce a standard stronger pulse train which is used for shifting the contents of the static register and for simultaneously enabling an, e.g. electro mechanical impulsing relay, and a control circuit for entering an interdigital pause into the static register whenever it has counted out an inserted digit. An off-normal contact simulation circuit enabled by the static register when this contains a digit, and a circuit for suppressing contact bouuce caused by depression of the push button provided. In addition, the initial lifting of a subscriber's handset causes all the shift registers and the clock pulse divider to be reset, and a start-code to be written into the set of parallel shift registers. When the first digit is subsequently keyed-up its binary equivalent replaces the start-code in these registers.