GB1518685A - Circuit arrangement for identifying code words - Google Patents

Abstract

1518685 Selective signalling PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 21 Aug 1975 [24 Aug 1974] 34781/75 Heading G4H In a circuit arrangement for identifying a series of unknown code words, a succession of parallel (reference) code words is read from each of two stores in turn, these words being serialized and then compared with the unknown code words to be identified. In a mobile radio telephone station, a multidigit call number is received followed by channel selection digit(s), each digit preceded by a start signal which starts a first clock pulse generator to produce a number of clock pulses equal to the number of bits in the digit. The clock pulses advance a counter once per digit to address a first store to read out the station's call number, serial by digit, parallel by bit, to a serializer (code converter) which converts each digit to serial by bit form, in which form the digits are compared with the received call number, the comparator resetting the counter on inequality. The clock pulses also go to the serializer and comparator. If the whole call number is equal, the comparator starts and controls a second clock pulse generator to supply the digits 0 to 9 in coded form from a second store, in turn, each digit parallel-by-bit, the digits being serialized in the serializer and then compared in the comparator with the (or each of the, in turn) channel selection digit(s), to obtain a match. The coding is such that this can be done by comparing the first incoming bit with the first bit of each digit from the second store in turn until equality is found, then comparing the second incoming bit with the second bit of the digit thus reached in the sequence 0 to 9, and subsequent digits, until equality is found, and so on for the remaining bit positions, the comparator controlling the second clock pulse generator as appropriate. The digit(s) in the second store thus reached is/are stored in a third store and used to select a channel. The station call number is sent as an acknowledgment as a frequency-modulated signal on the voice channel carrier, using the first clock pulse generator, counter, first store and serializer.