Bike speedometer (CB20497E)

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

Telephone dialer extension (CB9299E)
Found in a Hands-On Electronics from the 90s, this circuit produces the dial tones of an old...
Multiple time base (CB7535E)
Found in Radio Electronics from the 90s, this circuit has several outputs with different pulse...
Telephone Call Indicator (CB17398E)
This circuit, found in 2002 documentation, triggers LEDs when a phone call is received. The LEDs...