Using the 723 integrated circuit, this power supply has the voltage determined by R2 and R3, which can be changed. The circuit is from a Radio Electronics magazine from July 1971.
This circuit for recognizing a frequency with a narrow range was found in Radio Electronics...
Any small sound amplifier from 200mW to 1W can be used in this simple circuit. Or circuit of two...
This Linear Technology circuit was found in a 1980s documentation. The circuit can swing up to a...