| 摘要 |
PURPOSE:To exclude address codes from a playback signal and to stop an abnormal sound and the motion of a woofer when there is no signal, by providing a control circuit for opening and closing a switch and a nonsound detecting circuit which sends a signal to said circuit. CONSTITUTION:The nonsound detecting circuit 6 is a circuit which adds, for example, an L-channel and an R-channel signal together and regards as a nonsound period when the level of the sum signal is less than a specific value continuously for a specific time or longer. In the nonsound period, a signal having, for example, a logical level ''1'' is outputted to a control circuit 7. If the sum signal rises above the specific level when the nonsound detecting circuit 5 judges the nonsound period, the circuit is reset and outputs a signal with a logical level ''0'' to the control circuit 7. The control circuit 7 closes a switch 8 in response to the signal of ''1'' to add the L-channel and R-channel signals and generate an address code ''0'', or opens the switch 8 in response to the signal of ''0'' to form a normal reproduction system. |
