AC voltage control (CB8904E)

This circuit was found in a 90s Hands On Electronics. The semiconductor component is a Triac of the time.

Cardiac Monitor (CB10961E)
This circuit was found in a 1987 magazine. It measures monitors the heartbeat through a...
3 MHz TTL Oscillator (CB5123E)
This crystal-controlled circuit was obtained from a 1980s documentation. The power supply should be 5...
Headphone Amplifier (CB14735E)
This circuit is from 1957 Raytheon documentation. The phone must be high impedance with 600 ohms...