Nippon Electric Co., Ltd.

Haruki Takai

Kotaro Kato

A clock signal reproducing network for PCM signal reception is capable of reproducing a clock signal even if the clock component is absent in the input digital signal for a prolonged period of time. The network includes a clock signal component extracting circuit and a bandpass filter for extracting and band-limiting the clock signal component in a received digital signal. An envelope detection circuit and a level decision circuit are connected to receive the output of the bandpass filter to provide a control signal to an output switching circuit. When the amplitude of the envelope of the filter output is high, the output of the bandpass filter is used directly as a reproduced clock signal. When the amplitude of the envelope is low, the clock signal obtained immediately before the filter amplitude becomes small is derived repeatedly from a delay circuit as a substituted clock signal.

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Tokyo, Japan

Haruki Takai