Two-tone solar buzzer (CB20493E)

This circuit was found in a 1991 publication. The transistor can be a general-purpose type.

Electrolytic recoverer (CB7074E)
This circuit aims to recover electrolytic capacitors by applying currents higher than normal for a...
Curve viewer on oscilloscope (CB23877E)
Published in Radio Electronics magazine in May 1963, the purpose of this circuit is to visualize the...
Instrumentation Amplifier (CB18979E)
This amplifier with very high input impedance was suggested by Texas Instruments in a manual of...