Heartbeat Detector (CB25472S)

This heartbeat sensor circuit was found in the July 1992 issue of Radio Electronics magazine. The circuit uses a 741 with a single power supply.

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Digital Clock Generator (CB24246E)
This TTL circuit is from a Radio Electronics magazine from February 1973. The circuit must be...
Operational RIAA Preamplifier (CB14846E)
Common operational amplifiers like the TL series, CA3140 and others can be used in this circuit...
Telegraphy Practice Oscillator (CB16348E)
This circuit uses only two common transistors and provides good audio power in a speaker. Readers who...