| 摘要 |
951,027. Testing regenerative repeaters. STANDARD TELEPHONES & CABLES Ltd. June 15, 1962 [June 16, 1961], No. 23116/62. Heading H4L. Relates to an arrangement for providing an indication of a fault in any one of a chain of regenerative repeaters in a pulse code modulation system. As shown, distorted incoming code pulses a are supplied to a limiter V providing re-shaped pulses b and with switch r in its normal position the pulses b are supplied via an AND circuit S, also receiving pulses c from a pulse generator O, to the output circuit, the regenerated signal being shown at d. The pulses c have a repetition frequency equal to twice that of the incoming signal and are compared in a phase detector Ph with the incoming signal to provide a control voltage controlling the frequency of the generator O and also energizing a relay coil R. Failure of the control voltage will cause the pulse generator O to oscillate at a frequency lower than its controlled frequency and characteristic of the repeater as shown at e. The relay coil R will be de-energized and will change over contact r so that the output frequency e after halving at T is applied as signal f to the AND circuit S, thus transmitting signal g as a fault indication to the next repeater, alternate repeaters being assumed to be attended. The circuit S may be a bi-stable flip-flop which is triggered to start an output pulse on the appearance of a pulse at S2 during the period of a pulse at S1 and terminating the output pulse on the appearance of the next pulse at S2 after the terminationof the pulse at S1. |
