Beacon with instrument (CB20495E)

This circuit causes an instrument needle to oscillate to signal an event. The circuit is powered by solar panel from 1 V.

300 to 3,000 Hz Speech Filter (CB6543E)
Found on an 80's Radio Electronics, this two-section circuit is designed to pass the frequency...
4093 Sine Square Converter (CB25324E)
We found this circuit in an article in Electronics Now magazine from March 1996. The frequency is limited...
Transistor Test (CB19458E)
This circuit was found in a French publication in 1981, but it can still be assembled with only...