Ultrasonic repellent 4011 (CB9385E)

This circuit was found in Radio Electronics from the 90s. The transducer is a tweeter and the power transistor must have a heatsink.

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9 V source from 3 V (CB20464E)
We found this circuit in recent English documentation. It can provide an output current between 9 and...
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In the figure we have the way to connect 6 solar cells in order to obtain higher voltage and...
Electronic voltmeter (CB23755E)
This circuit was found in Radio Electronics magazine from August 1966. The transistors are from...