Photocardiograph (CB21738E)

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

Battery Charger (CB4388E)
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
Ramp generator with the 555 (CB7598E)
We found this circuit on an Elektor from the 90s. The frequency is given by capacitor C1. The...
5 V x 10A power supply (CB15926E)
This powerful regulator, shown in the figure is for 5V (TTL) is suggested by Motorola and makes use...