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 was found in Radio Electronics from the 90s. The transistor is for general use. The...
We found this circuit in a 2005 Linear Technology application manual. The circuit makes use of a...
This circuit is from 1971 American documentation. Transistors are still common except for 2N2060...