This circuit was found in a Hands On Electronics from the 90s. It turns on an LED to indicate that the phone is in use.
This small FM transmitter, with a few tens of meters in range, is powered by a 9 V battery. The...
The National Semiconductor LM377 integrated circuit consists of a low power audio amplifier. This...
This power supply, which is a small inverter, runs on a single large 1.5V battery providing 6V and...