Anti-tamper circuits

If you take a closer look at our system, you might realize that depending on whether you are detecting normally open or normally closed sensor switches, it is possible to tamper with the sensor channel by simply cutting the wire. So, in the case of a normally open switch, it wouldn't activate the monitoring system if the wires were cut, as it would always appear to be open, even if the switch was closed.

To mitigate this, most alarm systems feature a 4-core wiring system to connect the sensor devices to the main control board—two cores are used to connect the sensor and two are used to create an anti-tamper loop, which then itself forms a sensor input for monitoring.

4-core alarm cable

Take a look at the following circuit so ...

Get Raspberry Pi: Amazing Projects from Scratch now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.