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.
This circuit uses two light-activated SCRs or LASCRs, uncommon components today. The power depends on...
This type of configuration can be seen elsewhere in this section. This is from a 1965 General...
Crystals from 100 kHz to 1 MHz can be used in this 1957 Raytheon circuit. 4 can have values...