** TL1-16 Dual Burglar Alarm
"SolderFree" Kit (parts only)

Price: $2.40

This very useful Burglar Alarm Kit works with a Normally-Open and a Normally-Closed circuit at the same time. Useful for Auto and Home Alarm Systems.

Theory: Closing switch S1 will put a positive voltage on the gate of the SCR causing it to conduct and to sound the alarm. Or, by opening the normally-closed switch S2, capacitor C1 will discharge, and put a positive pulse on the gate of the SCR causing it to conduct.

The only way to stop the SCR from conducting, once it has started to conduct, is to remove power from the circuit.

Thus, even if the sensor switches S1 or S2 are opened or closed again, the alarm will not turn off.

The only way to RESET the alarm is to disconnect the battery.