Light beam switch (CB21413E)

This circuit was obtained from a 1965 General Electric SCR manual. The components are from the period.

Telephone Bell (CB25683E)
This additional bell circuit was found in the February 1994 Electronics Now magazine. The...
Delayed Reed Relay (CB12185E)
A delay of a few seconds to a few tens of seconds can be achieved with this circuit found in a...
Single Transistor Alarm Circuit (CB24372E)
This circuit uses a transistor to trigger the alarm from a low quiescent current sensor. The relay...