Found in an Electronics World of 1968 this circuit can use current SCRs and the diodes are according to the lamp. The Circuit only works with incandescent lamps.
A touch in this circuit turns-on the lamp or the relay. Power supply is according the lamp or...
The transducer used in this configuration that appears elsewhere on this site is a piezoelectric...
You can measure capacitances across a large range of values using the AC Power line frequency as...