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 can be used as an amplifier for musical instruments or even with your cell phone. The...
This circuit, which can act as a shield, was found in a 1970s American documentation. The...
This timer produces a continuous sound at the end of the timer set in potentiometer RV1. The...