SIGNAL SYNCHRONIZING CIRCUIT OF PRIVACY CALL COMMUNICATION EQUIPMENT

摘要

PURPOSE:To eliminate deterioration in reproduced sound quality attended with synchronous error by inserting a synchronous protection circuit in between a gate signal demodulation circuit and a trigger generating circuit at the reception side to prevent the synchronous error due to noise. CONSTITUTION:An RS-FF24 of the synchronizing protection circuit 23 inserted in between the gate signal demodulation circuit 18 and the trigger generating circuit 19 at the reception side is set by a gate signal Gm from the circuit 18 and reset by the output of a synchronous lock ON/OFF control circuit 25. The output of the FF24 of the circuit 25 is controlled by a gate signal Gr from a gate signal generating logic circuit 26 to control the effectiveness of the set input of the FF24. Then the masking processing by the gate signal Gr is executed at the synchronous lock state and only the synchronizing signal is selected as the set signal from the gate signal Gm on which a noise is superimposed. Al the gate signals Gm are used as the set signals when the synchronous lock is in the off state to prevent generation of synchronous error due to noise.