| 摘要 |
PURPOSE: To prevent useless power consumption by supplying a bias power source to a buffer only when the decoder de-scrambles the scramble signal during the time when the power switch is turned off. CONSTITUTION: When the decoder de-scrambles the scramble signal while the power switch of a video tape recorder is turned off, the decoder supplies a de-scramble signal to the buffer 1g through a connector 1b and further gives a discriminating signal exhibiting that de-scrambling is already performed to a switching circuit 12 through a connector 1b. In the switching circuit 12, this discriminating signal makes a t transistor T4 conducting and, in response to this, a transistor T3 becomes conducting. Accordingly, a rising 12V bias power source voltage is impressed on the buffer 1g irrespective of the on/off condition of the power switch to activate the buffer 1g. Through this, the descramble signal supplied to the buffer 1g is amplified and outputted to a TV receiver through a connector 1a.
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