SIGNAL DETECTING CIRCUIT

摘要

PURPOSE:To attain proper reception by causing prescribed oscillation depending on the carrier level detection state of a carrier signal separated from a voice signal being the result of modulating the mixture of the carrier signal and the voice signal. CONSTITUTION:A reception circuit 4 receiving a voice data (d) separates (demodulates) a voice signal (h) from a data received by a photodetector and sends the result, and separates a carrier (e) and sends the result to a carrier level detection circuit 5. The carrier level detection circuit 6 always monitors the level of the carrier (e) and sends an oscillation request signal (f) to an oscillation circuit 6 when the level reaches a prescribed or below. The oscillation circuit 6 is oscillated as specified and sends an oscillation signal (g) to the reception circuit 4. Thus, normal speech is attained.