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.
In the figure we have the way to increase the current capacity of an operational amplifier. The...
We found this circuit in a 1982 documentation, but the circuit can still be easily assembled, as the...
Found in an Electronics World of 1968 this circuit can use any SCR and diodes depending on the...