| 摘要 |
PURPOSE:To facilitate the gain adjustment and to attain remote control by using a pushbutton switch, an up-down counter operated in response to the operating mode and a semiconductor variable resistive element in response to the count. CONSTITUTION:In applying intermittent control to the pushbutton switch 12, a monostable multivibrator 13 is activated continuously, a logic '1' is given to an AND gate 10, the up-down counter 15 receives a pulse of a pulse generator 9 and its count is incremented. In releasing the switch 12, the counter stops at the count. When the count reaches 15, the count is stopped. A decoder 19 updates its decoding in response to the count and its signal is converted into a digital level signal by a resistance circuit network 20 and given to a semiconductor variable resistive element (FET) 8 through a voltage controlled circuit 21. The resistance of the FET 8 is increased gradually as the count is incremented and the gain of amplifiers 2A, 5A and the gain at that time is maintained by releasing the switch 12. In operating the switch 12 consecutively, an integration circuit 14 gives a level '1' to the AND gate 11, the count of the counter 15 is incremented and the gain is deceased.
|
