Signal Tracer and Capacitor Tester (T1241E)

This mains powered two-in-one instrument was found in a Radio Craft from March 1948. The headphone must be high impedance.

High Sensitivity Fan Control (CB15521E)
Another way to increase the sensitivity of the circuit with the amplification of the sensor...
Astable with crystal (CB24937E)
We found this circuit in the Radio Electronics magazine of January 1986. The frequency is given by the...
Pulsating Buzzer (CB24836E)
This circuit was found in the September 1984 issue of Radio Electronics magazine. The circuit is...