Written in an article in Radio Electronics magazine in April 1987, this circuit triggers an alarm via a relay. Details of the sensor are given in the article.
This circuit of the 1970s uses Germanium transistors. Changes can be made to use silicon...
This circuit was found in an integrated circuit manual from the 1980s. The circuit can be designed...
Found on a 1965 Radio Electronics, this circuit fires a signal xenon lamp applied to the SCR from...