Found in old documentation, this circuit can generate pulses from 400 to 4000 Hz with active cycle control from 1% to 99%.
We found this heart rate sensor circuit in a Popular Electronics from the 90s. The placement of...
This circuit, found in an old magazine of the year 1968, uses a Power germanium transistor. This...
This project came out in an article of mine (Newton C. Braga) in the Popular Electronics magazine of...