| 摘要 |
PURPOSE:To switch sound recording and reproducing operation electronically by a switch having the small number of circuits by supplying electric power controlling a switching circuit for reproducing and sound recording amplifier circuits by using a switching transistor (TR) to be controlled by a sound recording and reproducing changeover switch. CONSTITUTION:When the sound recording and reproducing changeover switch 24 is in a reproducing position, the switching TR25 is in reverse bias, i.e. disconnected state, so that control voltage is not impressed from a power supply line 28. Consequently, a reproducing operation controlling TR30, the 1st sound recording operation controlling TR32, a bias controlling TR36, and a controlling TR38 are disconnected and the 2nd sound recording operation controlling TR35 is connected. Since the TR30 is disconnected and the TR36 is connected, a reproducing amplifier circuit 4 is actuated and a sound recording amplifier circuit 13 is disabled. Since the TR36 is disconnected, a bias oscillating circuit 22 is disabled and the 2nd terminal 3 of a magnetic head 1 for sound recording/reproducing is earthed by the sound recording and reproducing changeover switch 24. |
