Silent alarm (CB22471E)

This circuit is from a Popular Electronics from 1992. The circuit powers an LED when triggered.

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...