GB1354805A - Pulse time coding arrangment - Google Patents

Abstract

1354805 Excitation function transmission STANDARD TELEPHONES & CABLES Ltd 16 Dec 1971 58427/71 Heading H4R [Also in Division G4] In a pulse time coding arrangement for transmitting, on an isochronous pulse transmission system, the time position of a pulse in an anisochronous pulse train, e.g. the excitation pulses of a speech signal, a marker pulse is transmitted, coincident with a system clock pulse and signifying the existence of an anisochronous pulse in the clock period preceding the clock pulse, together with a group of pulses specifying the position of the anisochronous pulse within the clock period. As described the occurrence of an anisochronous pulse sets a bi-stable 20, Fig. 2, which via a second bi-stable 21 enables AND gate 23 to allow pulses at 8 times the basic clock rate to step counter 24 until the bi-stable 21 is reset by the next clock pulse, so that counter 24 will indicate the time between the anisochronous pulse and the following pulse. The following clock pulses are also applied, via AND gate 22 which is enabled by the output of bi-stable 20, to a counter 25 and to a gate 28. The first clock pulse after the anisochronous pulse is fed to the output as the marker pulse via OR gate 27 and AND gate 28, enabled by the first clock pulse stepping counter 25 into its "one" state. The following three clock pulses step counter 25 back to its initial state, with the pulses being transmitted to the output or not dependent on the count existing in counter 24 which sets gates 29 to 31 appropriately so that the three clock pulses following the marker pulse indicate the position of the anisochronous pulse relative the marker pulse. The third clock pulse after the marker in restoring counter 25 to its initial condition resets bi-stable 20, and hence counter 24, to restore the whole apparatus to its initial condition. At the receiver, Fig. 3, the marker pulse, via OR gate 37, starts counter 32 counting the clock pulses so that the succeeding pulses are fed to the appropriate stages of counter 33 to set the counter to the condition corresponding to the incoming time indicating pulses. When all the stages of counter 33 have been appropriately set counter 34 will be restored to its original condition, enabling AND gate 39 so that counter 33 will be counted on, by the complement of the count set in it, until it is restored to its original condition, when the gate 38 output will go to "0", providing an excitation pulse generation signal. The output from gate 38 is fed to gate 39 to prevent further incrementing of counter 33. The pulses, when referring to the excitation function of a speech signal, are time multiplexed with information concerning the speech spectrum.