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.
Available at Mouser Electronics this component of Diodes Incorporated consists of a voltage...
This detector is from the 1990 Motorola Dataar Databook, but can be adapted to work with more...
This circuit doubles and reverses the polarity of voltage Ve which can be between 5 and 15 V. The...