CQR Grade 2 Door Contact, Surface, Multi Resistored, Brown SC517/BR/MULTI/G2/EN

What this door contact is for

A door contact tells an alarm panel that a door or window has opened. One housing holds the switch and the other holds the magnet, and parting them changes the circuit.

This CQR contact is for wired systems in domestic and commercial alarm circuits. The brown housing suits darker frames, and the links on the board let one part serve different resistor schemes.

How it works

• Normally closed: the circuit stays closed while the magnet sits beside the contact housing, and goes open when the magnet housing is moved away.
• End of line resistors: these let a panel tell a healthy circuit from a cut or shorted cable. Links are cut to leave the value the panel expects.
• Double pole: the other wiring method, where alarm and tamper run as separate pairs. Four terminals allow for that.
• Combination values: the 4K7 and 4K7 option uses the alarm link of type B and the tamper link of type E.

Where to use it

CQR shows it on casement and sash windows, patio doors and residential doors. Class II is for use indoors, so a door open to the weather needs checking against that rating and the -15° C to +40° C range.

The grade limit matters for the whole system. It can be used in installations up to and including grade 2, and the guide to intruder alarm standards explains what those grades mean.

What the figures mean in practice

• Min Close and Max Open: the gap at which the contact makes as the door shuts, and the gap at which it opens as the door moves. A door that moves in its frame can use up that allowance.
• 500mA @ 12Vdc: the limit for the switch itself. Keep anything wired through the contact inside that figure.
• Steel frames: mounting on a ferrous surface will reduce the gap figures, so test it in place.

Installing it

• Tamper plate: the separate anti tamper plate must be secured with its own screws before the main case is fitted.
• Board position: refit the board nearest to the arrow with the tamper switch facing outwards, which ensures maximum operating gap.
• Links: cut the links for the chosen scheme. For double pole, cut L1 and L2, with alarm on T3 and T4 and tamper on T1 and T2.
• Fixings: both housings fix on 26mm centres, so mark the magnet position with the door shut.

Planning your system

The contact needs an alarm panel zone and a run of alarm cable with enough cores for the chosen scheme. Check the panel's own manual for its resistor values before cutting links.

Newer panels may not be covered, so check yours. Comparable parts sit under door contacts and burglar alarm sensors.