DH-58 Rolling Door Magnetic Contact – NC Metal Door Sensor

Description

The DH-58 Rolling Door Magnetic Contact (NC) is a heavy-duty security sensor designed specifically for rolling shutters, garage doors, and industrial gates.

Unlike standard door contacts, this model features a strong metal housing and larger detection gap, making it ideal for environments where larger door movement occurs, such as warehouses, factories, and commercial shutters.

The sensor operates using a magnetic reed switch and magnet pair. When the door is closed, the magnet keeps the circuit closed. When the door opens and the magnet moves away, the circuit opens and sends a signal to the alarm panel.

The zinc alloy metal casing provides durability and resistance against harsh environments, making it suitable for industrial security installations.

Built for rolling shutters and metal doors. The DH-58 is a heavy duty magnetic contact designed for the doors that defeat ordinary sensors: steel rolling shutters, roll up godown doors, metal gates, and warehouse entrances. Standard plastic door contacts fail on these because the gap is wide, the door moves and vibrates, and surrounding steel interferes with the magnetic field. This unit is built specifically for that job.

Why shutters need a different sensor. A rolling shutter does not close with the precision of a hinged door. It settles differently each time, sits with a wider and less consistent gap, and rattles in wind. A sensor designed for a wooden office door will report false openings or miss real ones. A shutter contact tolerates a wider operating gap and is housed to survive being knocked, which is why it stays reliable on a shop front that opens and closes twice a day, every day.

Where it is normally used. Shop shutters on main roads, warehouse and godown roller doors, factory gates, garage doors, and any steel door where a normal contact has already failed. In Pakistan the most common installation is a shop shutter wired to an alarm panel so the owner is alerted if the shutter is lifted after closing.

NC contact and why it matters for security. The DH-58 is a normally closed contact, which is what alarm systems expect. In an NC circuit, current flows continuously while the shutter is shut. Opening the shutter breaks the circuit and triggers the alarm. Critically, so does cutting the cable, which means tampering with the wiring sets the alarm off rather than silently disabling it. A normally open contact does not offer this protection, and it is the reason NC is standard for security applications.

Mounting on steel without losing reliability. Metal is the enemy of magnetic sensing, so mount the contact so the magnet and sensor face each other directly rather than at an angle. Where reliability is marginal, fit both halves on thin non-metallic spacers to lift them slightly off the steel surface. Position the pair away from the shutter guide rails where movement is greatest, and check alignment again after a few weeks of use once the shutter has settled.

Getting the gap right. Every magnetic contact has a rated operating gap. A shutter that sits loosely may exceed it, producing an alarm that triggers every time the wind moves the door. If your shutter has significant play, tell us before ordering and we will confirm whether this model’s gap tolerance suits your installation or whether you need a wider gap unit.

Cabling on a moving door. The cable must run to the fixed frame side, never to the moving shutter. Route it in conduit and leave no exposed run, because an accessible sensor cable on a shop front is the first thing an intruder will cut. On a shutter that is opened daily, secure the cable properly so repeated vibration does not eventually work a connection loose.

Connecting it to your alarm. Wire the contact into a zone on your burglar alarm panel so a shutter opening triggers the same siren and notification as any other zone. Where you want a phone alert rather than a siren, it can also feed a dialler or a smart relay module. ZZ Marts stocks the panels, sirens, diallers, and cabling to complete the installation.

Power and load shedding. Wired contacts draw their power from the alarm panel and need no batteries of their own, so they keep working as long as the panel does. Fit a backup battery at the panel and your shutter stays monitored through load shedding, which is exactly when an unmonitored shutter is most exposed.

Wired rather than wireless, and why that is right here. For a shop shutter, a wired contact is the better choice. It never needs a battery change, does not depend on WiFi or internet, and cannot be defeated by jamming or a router being switched off. Wireless sensors suit interior doors and rented spaces; a commercial shutter protecting stock deserves a wired connection to a proper panel.

Will it work on my shutter? Send us a photograph of the shutter and the gap when closed on WhatsApp and we will confirm before you order.

Can it be used on a normal door? Yes, though for a standard wooden or aluminium door a smaller recessed or surface mount contact is usually neater and less expensive.

Does it need its own power supply? No. It draws power from the alarm panel it connects to.

How many do I need for a wide shutter? One contact per shutter is normal. Very wide shutters that lift unevenly sometimes justify two, which we can advise on.

Buying from ZZ Marts. Available at our Karachi (Saddar) and Lahore stores with delivery across Pakistan, supplied by Zam Zam Traders, trading in security hardware since 2005. We also stock recessed and surface mount door contacts for standard doors, wireless Tuya door sensors, alarm panels, sirens, and cabling. Tell us your shutter type and what you are connecting to and we will specify the whole job rather than just the sensor.