This circuit was found in American documentation from the 1980s. The integrated circuit used is a voltage comparator of the time. Modern equivalents can be tested.
This interesting source of very low voltage for reference finds applications in the...
This sonic switch, sound relay or simply vox uses a medium impedance speaker as a microphone. The...
Using red LEDs with ignition voltages of the order of 1.5 V we can make a multiple voltage...