This simple sensitive circuit was suggested in a July 1992 Radio Electronics issue. The relay is a double-contact changeover relay. Sensitivity adjustment is made at R2.
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We found...
This circuit is from a Radio Electronics magazine from February 1992. The circuit has the effect...
This simple circuit tests both monophonic and other two-wire audio cables. The circuit is powered...