Muting circuit in a PCM recording and reproducing apparatus

In a PCM recording and reproducing apparatus wherein digital data units representative of an analog audio signal are constructed into a data unit sequence with an error detection code being added to each of said data units for detecting coding errors within at least each of said data units, and data synchronizing signals are inserted one for every predetermined interval of said data unit sequence to constitute a PCM data sequence, said PCM data sequence being recorded on a record medium and reproduced from said record medium, and said data units are retrieved from said reproduced PCM data sequence and the retrieved data units are converted to an analog signal to reproduce the original analog audio signal;

• a muting circuit comprising;
• (a) error detection means for detecting coding errors in said data unit by said error detection code and producing an eror detection signal each time said coding error is detected;
• (b) separation means for separating said data synchronizing signals from said PCM data sequence;
• (c) count means for counting up said error detection signals, said counting means being cleared by said synchronizing signals;
• (d) first control means for producing a first control signal when the count of said count means reaches a first predetermined count;
• (e) second count means for producing a second control signal when the count of said count means immediately before cleared by said data synchronizing signal is equal to a second predetermined count smaller than said first predetermined count;
• (f) third control means adapted to receive said first and second control signals for continuously producing a muting signal when said first control signal is received and blocking said muting signal when said second control signal is received;
• and
• (g) muting means inserted in an analog audio signal path of a reproducing unit for interrupting the transmission of the analog audio signal in response to said muting signal.