Bike speedometer (CB20497E)

This circuit can be powered by a solar cell. The circuit is from a 1991 documentation having a phototransistor as sensor.

Headphone output (CB23841E)
In the figure we have the adapter circuit for connecting a headphone to the output of a stereo...
Square and triangular generator (CB24196E)
Found in the June 1972 issue of Radio Electronics magazine, this circuit generates signals that...
Stethoscope (CB12295E)
The output of this circuit must be connected to the input of an audio amplifier. The microphone is a small...