This circuit is from 1999 documentation. However, it can still be easily assembled, as all components used are common. The sensors can have their quantity increased, being connected in parallel.
This circuit, from the 90's, is intended for operation with vinyl record players of the time, as...
Using a zener diode it is possible to change the linearity of the scale of an analog instrument by...
Found in American documentation from the 1980s, this circuit prolongs the ringing of a doorbell or chime...