This simple circuit was found in a Japanese magazine in 1967. The circuit is listening on a headset and the coil is 50 + 50 turns of wire 28 or thinner on a ferrite rod.
The sensor for this alarm is an LDR and it consists of an oscillator that goes into action when...
This circuit tests quartz crystals of frequencies between 100 kHz and 10 MHz. The circuit is from...
We found this FM transmitter circuit with the 2N2218 transistor in a documentation from the 90s....