Crystal oscillator (CB9504E)

This circuit was found in a 90s Popular Electronics. It can generate signals from 3 to 10 MHz.

Going Astern Alert (CB4774E)
We found this circuit in a Popular Electronics of the 90s. The circuit still uses light bulbs, but...
Alarm and current sensor (CB5285E)
This circuit is from Linear Technology 2005 documentation. The circuit is based on company...
15 V x 1 A power supply uA723 (CB19023E)
The integrated circuit used in this power supply is no longer very common in power supplies today....