Photocardiograph (CB21738E)

We found this circuit in a 1969 Popular Electronics. It measures the heartbeat by changing the transparency of the finger.

Demonstration Microchip Boards of Consumer Monitors MCP39F511
July 2017 - Microchip's new MCP39F511 demonstration and development boards, which consist of...
Dual temperature and level control (CB9474E)
This circuit, which controls both the temperature and the level of a liquid in a reservoir, was...
LED Constant Current Source (CB12062E)
This circuit provides a constant current of 1 mA, stabilized by an LED, which can be equivalent to that...