This sensitive circuit was found in the June 1995 Electronics Now magazine. R1 can be from 10k to 1M depending on the desired sensitivity. Power is supplied by the relay.
This conventional astable uses two NPN transistor and was found in a publication of the year 1968. The...
This simple effect circuit for musical instruments and stereos was found in a 1987 publication. Powered by...
This circuit is a suggestion from a Radio Electronics from October 1964. We found it in the patent...