This circuit uses an optical coupler called Raystor created by Raytheon in the 1960s. The circuit uses components from the era that can be changed. The current is low.
This circuit was found in an old American publication. The integrated circuit used is no longer easy...
This circuit is from 1976 documentation. It uses the operational amplifier 709 which is no longer...
This circuit produces the sounds of the two types of siren switched by S3. The circuit is from...