This interesting circuit with a neon lamp and a transistor was found in Radio Electronics magazine from February 1968. The transistor is a special type of high voltage at the time.
This circuit produces a clef sound when a pulse is applied to its input. The damping effect is...
This circuit can serve as the basis for a simple phone. The LM10 is not common today, but the...
This is a possible circuit for the receiver of the previous circuit. Other circuits can be found...