| 摘要 |
PURPOSE: To narrow an installing area on a front panel by using the connection jack of a headphone also as that of a microphone. CONSTITUTION: The signal terminal 1a of a jack 1 is connected to the movable contact of a changeover switch 4. Moreover, the fixed contact 4a of the changeover switch 4 is connected to a microphone input amplifier 5, and the fixed contact 4b to the left(L) channel output amplifier 6 of the headphone. Also, the second signal terminal 1b of the jack 1 is connected to the right(R) channel output amplifier 8 of the headphone via a switch 7. Also, the ground terminal 1c of the jack 1 is grounded. Moreover, the output of an arbitrary oscillator 9 is connected to the second signal terminal 1b. Also, the output of the oscillator 9 is connected to a signal detection and hold circuit 11, and the output of the signal detection and hold circuit 11 is connected to the changeover switch 4 and the control part of the switch 7. |
