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.

| Clique na imagem para ampliar |

Sine and Cosine Audio Generator (CB21337E)
Found in an old American publication, this circuit is intended for audio experiments. The...
Step Generator with SN75489P (CB24560E)
This circuit was found in the June 1978 issue of Radio Electronics magazine. The circuit is...
Band Pass Filter (CB15477E)
The circuit shown in the figure is suggested by Texas Instruments in its Linear Circuits...