| 摘要 |
PURPOSE:To simplify the constitution by disusing an independent switch interlocking with an external mike connecting jack and controlling turning-on and off of a transistor (TR) for muting directly by a power +B applied to a hot-side terminal of the external mike connecting jack. CONSTITUTION:The base of a TR9 is connected to a hot-side terminal (b) constituting an external mike connecting jack 1 through a resistance 8. Consequently, the power +B is applied to the base of the TR9 through a resistance 7, the external mike connecting jack 1, and the resistance 8 when an incorporated mike 3 is used; and when the incorporated mike 3 is used, the TR9 is turned on, and no output appears in a monitor output terminal. When an external mike is used, the TR9 is turned off because the hot-side terminal (b) of the external mike connecting jack 1 and the third terminal (c) are disconnected from each other, and the output appears in the monitor output terminal 10 and a recording signal output terminal 11. Thus, a monitor switching device is constituted easily without the independent switch. |
