GB861515A - Improvements in or relating to timing circuits - Google Patents

Abstract

861,515. Telephone transmission systems. WESTERN ELECTRIC CO. Inc. Dec. 10, 1958 [Dec. 24, 1957], No. 39824/58. Class 40 (4). A circuit for timing an operation comprises a generator for cyclically generating a succession of code groups, a store into which is entered that code group occurring at the beginning of the operation, means for translating the code groups into groups corresponding to later positions in the cycle, and a comparator which upon receiving identical code groups from the store and the translator emits a signal to terminate the operation. As described, the successive code groups are binary representations of numbers 1 . . . 8 and the translator is a logic circuit whose binary output represents a member 2 more than its input. The invention is applied to the timing of a talker connecting signal in a TAS1 system such as that described in Specification 845,174. As shown identities, in the form of 7-digit binary numbers, of newly active talkers, are queried in a register 322 preparatory to insertion into a free time slot in a circulating store 309, which has a slot for every channel. A free channel is indicated by the digits 00 in the channel status portion of the store and when these are received by the translator 310, an output on lead 311 opens the switch 315 to admit the identity of a talker to the store and also to replace the 00 by 01. Simultaneously a three-digit binary number is admitted to the right-hand side of the store from a binary counter stepped once per millisecond by the oscillator 325 in an 8-millisecond cycle. This binary number is fed to the ADD 2 logic circuit 327 whose output feeds one side of the comparator 328. After 6 milliseconds the output of the logic circuit will be identical with that originally stored in the circulating memory. The latter circulates at 8 revolutions per millisecond so that the contents of all its time slots are compared with the each output from the logic circuit, and when identity is obtained the comparator emits a signal on lead 329. Meanwhile, with 01 in the channel status portion, translator 310 when fed from this time slot opens switch 333 to feed the talker identity to a " connect " signal source 323, which emits pulses on 324 modulated by combinations of seven tones in accordance with the talker's identity. These are fed over the assigned channel to the receiver as described in Specification 845,174. At the end of 6 milliseconds the output on lead 329 causes the substitution of 11 for 01 in the channel status portion of the memory to terminate the " connect " signal. The remainder of the operation is as described in Specification 845,174. Specification 781,622 also is referred to.