Magnetic contacts: choosing the right model and fitting it correctly

The magnetic contact is the simplest, cheapest and often most effective detector in an installation: it reports the opening of a door or window before the intruder even enters the protected volume. You still need to choose the right model and fit it properly.

How it works

A contact consists of a reed switch and a magnet. As long as both are aligned, the circuit is closed; on opening, the magnet moves away and the panel sees the break. The operating distance, or gap, is the key figure on the datasheet: from a few millimetres for a flush model to several centimetres for a gate contact.

Choosing the model for the opening

The magnetic contacts range in the catalogue covers these cases, from the flush RS30 model to security contacts for heavy doors.

Fitting rules

1. Fix the reed switch on the fixed part (frame) and the magnet on the leaf: the cable must never move.
2. Place the contact on the opening side, opposite the hinges, where the travel is greatest.
3. Respect the alignment and the manufacturer's gap, allowing for the play of the door once locked.
4. Use the end-of-line resistor required by the panel to detect a cut or short circuit on the cable.
5. On exposed openings, prefer a model with tamper protection (pull-off contact).

Common mistakes

• Magnet on the fixed part and reed switch on the leaf: the cable breaks within months.
• Surface contact on a door that warps with humidity: the gap becomes insufficient in winter.
• Steel screws under the magnet: the field is deflected and the contact becomes erratic.
• Forgetting the toilet window or the roof hatch: yet these are the preferred entry points.

Combined with one or two well-placed volumetric detectors, a set of contacts on all exits provides reliable perimeter protection, even with an entry-level panel.