Bike speedometer (CB20497E)

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

Two Transistor Siren (CB4210E)
This well-known siren configuration using complementary transistors is from a 1980s documentation. The...
Light Beam Operated Relay (CB4956E)
This circuit was found in an old American magazine and could make use of more modern components...
RIAA Preamp (CB1260E)
This circuit is from the Philips integrated circuits manual of 1990. It is intended for magnetic...