This sensitive bio-monitoring circuit was found in the December 1984 issue of Radio Electronics magazine. The circuit is powered by a 9 V battery and uses a low-impedance headphone output.
We found this circuit in an English magazine from 1980. The circuit can be easily assembled even...
This circuit appears at various points in this section and on this site, with minor variations. It uses the...
E) This circuit uses a reversible double contact relay to obtain the trigger lock with the...