Damped sound (CB22470E)

This circuit generates a tone of a bell and can be used in this type of application. The circuit is from a Popular Electronics from 1992.

Differential Amplifier (CB19913E)
The operational amplifier used in this circuit is not common today. The circuit has an input...
Adjustable time delay (CB20367E)
This circuit activates a relay with a delay that can be adjusted in a range of values that depends on...
ouch Switch (CB15052E)
T This circuit produces an audible signal when someone touches the sensor, or even approaches. The...