Practice code oscillator (CB21696E)

In the figure we have an astable multivibrator driving a speaker to produce audio signals for Morse code practice.

Metal Detector (CB5334E)
The search coil of this detector consists of 140 turns of wire 18 in an 8 inch diameter form. The...
Segment decoder (CB6601E)
This circuit was obtained from a 1966 General Electric documentation. It can serve as a basis for...
Extremely low power alarm C106 (CB24134E)
The quiescent current of this alarm is in the order of microamps and the same is true for the...