The input and output frequencies of this circuit depend on the coils and capacitors of the tuned circuits. The circuit is from Electronics Now magazine, February 1997.
This circuit was found in a Popular Electronics from the 90's. The output signal can be applied to a...
A small loudspeaker (2.5 or 5 cm) can be used as a low impedance microphone. A preamplifier and...
This flip-flop circuit with general purpose transistors was found in American documentation from...