This circuit can be used as an answering password system in a store, office, or other location. The circuit is from Intersil using components of the time. The circuit is from the 80's.
We found this circuit in a 1997 publication, but by the components used it can still be assembled today...
The circuit below was suggested by the Motorola Linear Databook of 1990. The component used is...
Found in a 1970s documentation, this circuit has a flat response from 15 Hz to 130 kHz. Modern...