| 摘要 |
PURPOSE:To prevent disturbance of a telephone call response by adopting the constitution that a power supply of an acoustic equipment allows power supply to stop automatically in response to a sound raised by a telephone set. CONSTITUTION:A telephone pickup installed at a suitable place of the telephone set is cnnected to an input terminal 3 and when a telephone call comes externally and bell rings, or a handset is hooked off and talking is started, the telephone pickup detects a low frequency signal of a telephone set and the signal is amplified by an amplifier circuit 4. The amplified low frequency signal gives an electric charge to a timer capacitor 15 by the operation of an input capacitor 13 and a transistor 14 to boost a terminal voltage. Thus, the DC voltage fed to the acoustic equipment 2 by the operation of the relay circuit 5 is interrupted by a relay contact 12 and the voice generated from a speaker 11 is stopped. Further, timer function 6 acts on keeping the said voltage off for a prescribed time even if the talking is intermitted. |
