We found this circuit in an Australian documentation from 1991. The circuit is suitable for SMD mounting thus making it very small. The circuit was sold in a kit at the time.
This circuit appeared in the July 1969 issue of Radio Electronics magazine. The sensor is an LDR....
For signals up to about 500 kHz modulated in amplitude and transmitted by the power network, the...
This circuit was found in the March 1984 issue of Radio Electronics magazine. The sensor is a...