Photocardiograph (CB21738E)

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

FM Transmitter with Auxiliary Input (CB17254E)
This circuit is from 2001 documentation and consists of a small FM transmitter with two inputs, one...
40 W Amplifier (CB16286E)
This amplifier, of excellent quality, provides a power of 40 W IHF, or 22 W RMS, in a load of 8...
5 V x 2 A Supply Regulator (CB19000E)
The input of this regulator can be between 7 and 12 V and the output is 5 V. The circuit is from...