This circuit uses an optical coupler to indicate a phone call through a lamp. The circuit is from a Hands-On Electronics from the 90s. The lamp must be incandescent.
Found in an Analog Devices documentation from the 90s, this circuit uses a component of the time,...
This circuit was found in Philips documentation from 1965. No information was given about the...
This circuit was found in the June 1990 issue of Radio Electronics magazine. Integrated circuits must...