Sensor for heart monitor (CB21075E)

We found this heart rate sensor circuit in a Popular Electronics from the 90s. The placement of the emitter and the receiver is important.

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Fast Photo Darlington (CB14647E)
With the circuit shown, you can have a fast response with a Darlington configuration. The circuit is...
Thermostat (CB24644E)
We found this multiple thermostat circuit in July 1980 Radio Electronics magazine. It uses...
EF MOSFETs Series with Diodes Fast Body (COM042E)
Mouser Electronics is already providing new MOSFETs EF SIHx28N60EF of Vishay series for voltages...