Photocardiograph (CB21738E)

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

Absolute Value Amplifier CA3140 (CB13841E)
This circuit is from the 1977 RCA Linear Integrated Circuits Manual. The circuit has a...
IR remote control emitter (CB7020E)
This circuit was found in 1980's Radio Electronics. The circuit produces a 1500 Hz modulate 35 kHz....
Triac Power Switch (CB25074E)
The maximum power of the controlled load depends on the triac used. The circuit is from a Radio...