Bike speedometer (CB20497E)

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

Power switch without RFI (CB21543E)
This circuit was found in an Electronic Design from 1967. The circuit uses two triacs being T2...
96 MHz Oscillator (CB9624E)
Found in old American documentation, this circuit can use crystals between 27.5 and 33 MHz...
Relay control (CB22286E)
This shield from the 60's uses a germanium transistor of the time and a common type of relay of...