Variable oscillator for code practice (CB7317E)

This circuit is from Popular Electronics from the 90s. The integrated circuit is not very common nowadays.

Proximity Relay (CB25343E)
This proximity relay circuit was found in the July 1990 Radio Electronics magazine. The supply...
AC sensitive relay (CB22173E)
This sensitive circuit for triggering relays was found in an old English publication. It works with...
LCD power supply with contrast control (CB8852E)
This circuit was obtained from a 90’s Linear Technology documentation. The circuit provides...