Based on the BA1404 integrated circuit, this circuit was found in the July 1992 issue of Radio Electronics magazine. The circuit is short range, but a power amplifier stage can be used.
This series sensor circuit is from 1995 Popular Electronics. The circuit can use any SCR and the...
The circuit is a multivibrator version using two NPN general purpose transistor. This circuit can...
This circuit is from 1976 documentation. It uses the operational amplifier 709 which is no longer...