Found in a 1967 Electronics World, this oscillator changes its tone when objects move in their environment. The output is made on a low impedance phone.
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
We found this circuit in a 1992 documentation. It can still be easily assembled today, as the...
The first circuit was suggested by Analog Devices (www.analog.com) in its Application Note AN-411...