| 摘要 |
PURPOSE:To prevent singing of a speaker due to the undesired signals by delaying the time point when a reset signal is supplied to a voice amplifier by a prescribed amount by means of a signal delay circuit and breaking the connection between the speaker and the voice amplifier. CONSTITUTION:A call signal A applied to a terminal IN is detected by a signal detecting circuit 1 and stored in a memory 4 after conversion into a logic level. At the same time, the detected signal A is delayed by the time T1 through a delay circuit 9 and applied to a gate circuit 10. A call signal B supplied next is detected by a signal detecting circuit 2 and stored in the memory 4 after conversion into a logic level. Then the output signal is applied to the circuit 10 from the memory 4. The circuit 10 is turned on with application of the signal delayed by the time T1 through the circuit 9. Then a gate circuit 7 is turned on to connect a speaker 8 and a voice amplifier 6. The voice signal supplied next is delayed by a second through a delay circuit 11 and delivered to the speaker 8. When the reset signal is detected by a signal detecting circuit 3, the memory 4 is reset to restore the circuits 10 and 7. Then the connection is broken between the amplifier 6 and the speaker 8. |
