This 1968 documentation circuit uses a relay to control loads up to 1 kW (depends on relay contacts). The supply voltage depends on the relay.
This different configuration for a crystal galena radio or modernized since a diode is used, has a...
This circuit is from 1990 documentation. When we press D1 the lamp remains on for a time interval that...
This version of the test lights a lamp when the ring touches the tortuous wire. The SCR can be the...