O'Reilly logo

Raspberry Pi: Amazing Projects from Scratch by Richard Grimmett, Matthew Poole, Arush Kakkar, Ashwin Pajankar

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

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 ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required