This audio oscillator is from a 1957 Raytheon publication. The tone generated depends on C2 and C2 and the handset must be high-impedance magnetic. Equivalent transistors can be tested.
This reflex receiver for the mid-wave range employs germanium transistors of the time. We found it in...
Using a 106 series SCR, this circuit was found in the May 1971 Radio Electronics magazine. The...
This circuit was found in an old manual of linear integrated circuits of the 80's. Equivalent...