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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Bass, Middle, and Treble Control with 741 (CB939E)
The original version of this circuit was obtained in a 1995 magazine Electronics Now. The magazine no...
Remote control extender (CB7026E)
We found this circuit in a Popular Electronics from the 80s. This circuit eventually doesn't work with...
3 kHz Variable Filter with the 741 IC (CB1460E)
This circuit was found in a 1975 filter cookbook. The operational may be others, but they should...