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.
This circuit was found in a 1960s General Electric unijunction transistor manual. The circuit can...
In the figure we have the configuration of a variable voltage regulator with two transistors and a...
This circuit was found in Raytheon's 1967 documentation. The circuit uses an operating of the era,...