GB982327A - Improvements in or relating to apparatus for supplying an electric timing signal under the control of an input electric signal - Google Patents

Abstract

982,327. Automatic plane control. GENERAL ELECTRIC CO. Ltd., and J. M. SMART. Nov. 8, 1962 [Nov. 8, 1961], No. 39998/61. Heading H3A. In a signalling system, e.g. a telemetering system in which a signal is transmitted which at each of a succession of equal intervals of time has one or other of two values, means are provided at a receiving station for producing a timing signal from the received signal for synchronizing the operation of the receiving station equipment. The intervals of time have a duration of 20 m.secs. and the received signal, appearing at terminals 37, 38, is applied via bi-stable circuit 36 to bi-stable circuit 41 which produces a short duration signal for priming bi-stable circuit 44 whenever a transition occurs in the value of the received signal. An oscillator 31 operating at either 598 or 602 c/s., i.e. nominally twelve times the recurrence frequency of the received signals supplies an output via squarer 33 to a twelve-stage circulating register 32 arranged such that at any time only one of its stages registers " 1 " while all remaining stages register " 0." Stages 4-7 of the register are connected to one input of bistable circuit 44 via gate 45 and stages 9-12 are connected to a second input via gate 46. The preferred times of occurrence of transitions in the received signal are when stage 8 of the register stores the value 1, if, however, oscillator 31 is operating at its lower frequency a time will be reached when a transition occurs when one of stages 4-7 registers " 1 " and a signal is applied via gate 45 to bistable circuit 44 when the circuit is primed by the transition signal. On switching the circuit produces an output which switches the oscillator to its higher frequency. Operation at the higher frequency eventually produces coincidence between a transition and the storing of a " 1 " in stages 9-12 when the oscillator is switched back to its low frequency via circuit 44. As each stage of the register stores " 1 " once every 20 m.secs. time signals for synchronizing the receiver equipment are obtained from leads 49-54. The oscillator, Fig. 1 (not shown), includes a transistor circuit which switches a small capacitor in parallel with the oscillator tuned circuit for lowfrequency operation. Specification 982,326 is referred to.