Many people ask about a 'standard' colour code for intruder alarms. The fact is that this has never been a part of any standard and each company has their own preferred colour code scheme.

On a fully-wired Intruder Alarm System, alarm cable generally forms the links between all of the devices 'in the field' and the control panel or zone expander. In the UK, the cable itself should conform to BS 4737 Part 3, which still applies to alarm cables and components.

You should always use the correct cable for the job - never use telephone cable or Category 5 or 6 cable for alarm system device wiring, since these cables contain solid-core wires which are much more liable to breakage at the screw terminal connections. This is why these cable types are usually terminated using Insulation Displacement Connectors (IDC).

Alarm cable colours and 'colour codes'

First of all, we should explore the standard wire colours available in the three most popular alarm cable variants:

4-core = Red, Black, Yellow, Blue
6-core = Red, Black, Yellow, Blue, White, Green
8-core = Red, Black, Yellow, Blue, White, Green, Orange, Brown

Using a 'colour code'

Let us examine a typical colour code scheme and the (usually historical) reasons behind it.

Every alarm cable has a Yellow wire and a Blue wire, and these are used for the zone circuit.

Red and Black is for DC power, i.e. 12 volts DC from the control panel, as this matches up with the battery + (red) and - (black) lead colours.

White and Green is the for the tamper circuit.

Working with the colour code above then, a BS EN 50131 Grade 1 magnetic door contact needs a zone circuit pair (Yellow/Blue) and a tamper circuit pair (White/Green). To stick to the colour code, we would use a 6-core cable and tuck away the spare Red and Black wires for future use.

A PIR movement sensor needs a zone circuit pair (Yellow/Blue), a tamper circuit pair (White/Green) and a DC power pair (Red/Black). While a 6-core cable would be perfectly adequate, we would recommend using an 8-core cable and tucking away the Orange and Brown wires for future use.

If you stick to this code, when you connect it up you can tell at a glance that all of your DC power wiring is Red / Black, zone wiring is Yellow / Blue and all of your tamper wiring is White / Green.

This should make the whole system easier to connect and repair.

TIP:

When you are preparing the cables at the control panel it is good practice to twist the circuit pairs of a cable before running them neatly to their connections and terminating. Any spare wires should be loomed and safely secured for future use. Individual cables should be clearly marked as to their use, i.e. dining room PIR, Front Door, etc. for ease of maintenance and future fault-finding.