Found in Mallory documentation from 1968 this circuit uses an integrated circuit from that time. The circuit has a flat response from 10 Hz to 700 kHz.
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...