Bike speedometer (CB20497E)

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

Solar radio (CIR21939E)
This primitive solar radio was found in a Gernsback publication from 1960. The transistor is made...
CMOS Injector (CB15763E)
The signal injector illustrated in the figure uses a single integrated circuit and generates...
Improved Red Alert (CB25341E)
This Star Trek red alert circuit was found in the July 1990 issue of Radio Electronics magazine. The...