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 receiver activates a relay from signals emitted by a 27 MHz modulated transmitter as...
This somewhat critical circuit was found in a year 2000 documentation. The frequency depends on...
This circuit can be used as a residential doorbell. We found it in an English publication from...