Reed Switches for Doors and Windows Explained

Reed switches are one of the most practical alarm sensors used in home and business security systems. They protect the perimeter of a property by detecting when a door, window, gate, roller shutter or access point is opened.

While motion detectors are designed to detect movement inside a room, reed switches help detect entry at the source. This makes them a valuable part of a well-designed alarm system for homes, offices, shops, warehouses and commercial premises.

In this guide, we explain what reed switches are, how they work, where they should be installed and why they are so important for doors and windows.

What Is a Reed Switch?

A reed switch is a magnetic contact used by a security alarm system to detect whether a door, window or other opening is open or closed. It usually has two parts: the switch and the magnet.

One part is fitted to the fixed frame, while the other is fitted to the moving door, window or shutter. When the door or window is closed, the magnet sits close to the switch. When the door or window opens, the magnet moves away and the alarm panel can detect the change.

Reed switches are commonly used on:

• Front doors
• Back doors
• Sliding doors
• Garage internal access doors
• Ground-floor windows
• Office entry doors
• Retail shopfront doors
• Roller shutters
• Warehouse roller doors
• Gates and restricted access points

How Do Reed Switches Work?

A reed switch works by using a magnetic field. When the magnet is close to the switch, the circuit remains in its normal state. When the protected door or window opens, the magnet moves away and the circuit changes state.

If the alarm system is armed, this change can trigger an alarm event. Depending on the alarm setup, the system may activate a siren, send an app notification, report to a monitoring centre or follow a programmed response pathway.

This simple design is one of the reasons reed switches are so widely used. They are reliable, discreet and suitable for a wide range of residential and commercial alarm applications.

Why Reed Switches Are Important for Doors and Windows

Doors and windows are common entry points for intruders. A reed switch provides direct protection for those openings by detecting when they are opened while the alarm is armed.

This is different from a motion detector, which usually only detects movement after someone has entered the property. A reed switch can help identify the entry attempt earlier, at the perimeter.

Key benefits include:

• Early detection: Detects when a protected door or window is opened.
• Perimeter protection: Helps secure entry points before movement occurs inside.
• Reliable operation: Simple magnetic contact design with long-term reliability.
• Discreet appearance: Recessed and surface mount options are available.
• Pet-friendly alarm design: Can reduce reliance on motion detectors in pet areas.
• Flexible use: Suitable for homes, shops, offices, warehouses and commercial sites.

Reed Switches vs Motion Detectors

Reed switches and motion detectors do different jobs, and many alarm systems use both. A reed switch protects a specific opening, while a motion detector protects an internal area.

For strong alarm coverage, a professional design may include reed switches on selected entry points and motion detectors in hallways, living areas, offices, warehouses or other internal zones.

Where Should Reed Switches Be Installed?

Reed switches should be installed on the entry points most likely to be used during a break-in or unauthorised entry. The best locations depend on the property layout, risk level and alarm design.

Homes

• Front door
• Back door
• Sliding doors
• Garage internal access door
• Ground-floor windows
• Laundry doors
• Home office entry points

Businesses

• Main entry doors
• Rear access doors
• Shopfront doors
• Storage room doors
• Office doors
• Warehouse roller doors
• Loading bay doors
• Restricted access areas

Types of Reed Switches

There are several types of reed switches available. The best option depends on the surface, location, installation style and whether the alarm system is wired or wireless.

Surface Mount Reed Switches

Surface mount reed switches are fitted to the visible surface of the door or window frame. They are one of the most common options for existing homes and businesses because they can be installed without cutting into the frame.

They are useful for:

• Existing homes
• Alarm upgrades
• Office doors
• Retail premises
• Windows where recessed installation is not suitable

Recessed Reed Switches

Recessed reed switches are installed into the door or window frame, creating a more concealed finish. They are often preferred for new builds, renovations and installations where appearance is important.

They are useful for:

• New homes
• Renovations
• Front doors
• High-end residential finishes
• Commercial fit-outs where a clean appearance is required

Heavy-Duty Reed Switches for Roller Doors

Standard door and window reed switches are not suitable for every opening. Roller doors, roller shutters and warehouse doors often need heavy-duty reed switches designed for larger moving surfaces and tougher environments.

Heavy-duty reed switches are commonly used on:

• Warehouse roller doors
• Factory doors
• Commercial shutters
• Loading bays
• Industrial units
• Storage facilities
• Large garage doors

Wired vs Wireless Reed Switches

Reed switches can be installed as wired or wireless devices, depending on the alarm system. Each option has its place.

Wired Reed Switches

Wired reed switches are connected back to the alarm system using alarm cabling. They are a strong option for new builds, renovations, commercial properties and homes where cabling is practical.

Wired options are often preferred when long-term reliability and reduced sensor battery maintenance are priorities.

Wireless Reed Switches

Wireless reed switches are used with compatible wireless alarm systems. They are useful for existing homes, apartments, townhouses and finished properties where running cables may be difficult.

Wireless options are flexible, but they do require battery checks and compatibility with the alarm panel or wireless hub.

Reed Switches for Pet-Friendly Alarm Systems

Reed switches can be very helpful in homes with pets. If a dog or cat moves around inside the home, relying only on motion detectors may increase the chance of false alarms. Reed switches allow the alarm system to protect doors and windows without depending entirely on internal motion detection.

For example, a pet-friendly alarm design may use:

• Reed switches on entry doors
• Reed switches on selected windows
• Garage door contacts
• Pet-friendly motion detectors in suitable areas
• Careful zoning so pets can remain in selected spaces

This type of design can provide better protection while allowing pets to move around more comfortably.

Reed Switches for New Builds and Renovations

New builds and renovations are the ideal time to plan reed switch cabling. Installing reed switches during construction can create a cleaner finish and reduce the need for visible surface-mounted devices later.

During a new build, consider pre-wiring reed switches for:

• Front door
• Rear sliding doors
• Garage internal access door
• Garage roller door
• Ground-floor windows
• External pedestrian doors
• Home office entry points

Planning early can also make it easier to combine reed switches with motion detectors, sirens, keypads, app control and back-to-base monitoring.

Reed Switches for Business Security

For businesses, reed switches help protect the perimeter of the premises. They can be used on shopfronts, offices, storerooms, roller doors, warehouses and restricted areas.

Business applications include:

• Retail shopfront doors
• Rear access doors
• Office entry doors
• Warehouse roller shutters
• Stockroom doors
• Server rooms and restricted areas
• Commercial gates
• Loading bay doors

When combined with motion detectors, CCTV and monitoring, reed switches can help create a stronger business security system.

Can Reed Switches Be Added to an Existing Alarm?

In many cases, yes. Reed switches can often be added to an existing alarm system, provided the alarm panel has available zones or the right expansion options. Wireless reed switches may also be available for compatible wireless alarm systems.

Before adding reed switches, check:

• The alarm panel brand and model
• Available wired zones or zone expansion options
• Wireless receiver compatibility
• The door or window frame type
• Whether cabling can be installed neatly
• Whether the reed switch should be surface mount, recessed or heavy-duty

CTC Communications can help recommend suitable reed switches and alarm accessories for your system.

Common Reed Switch Installation Mistakes

Reed switches are simple devices, but they still need to be installed correctly. Poor installation can cause false alarms, unreliable detection or missed alarm events.

Common mistakes include:

• Poor alignment between the magnet and switch
• Using the wrong reed switch type for the door or window
• Installing a standard contact on a roller door that needs a heavy-duty contact
• Running cables where they can be damaged
• Not testing the device after installation
• Not checking wireless battery condition
• Not programming the correct alarm zone type

Professional Installation Is Recommended

Professional installation is recommended for reed switches because correct placement, alignment, wiring and programming are essential. An experienced installer can choose the right sensor type, confirm compatibility and test each protected opening.

Professional setup can help with:

• Choosing the right reed switch for each door or window
• Neat installation and cable routing
• Correct switch and magnet alignment
• Programming each alarm zone properly
• Testing open and close events
• Reducing false alarms
• Integrating reed switches with app alerts or monitoring where supported

Why Choose CTC Communications for Reed Switches?

CTC Communications supplies a wide range of security accessories and alarm accessories for homes, businesses and commercial security systems.

Our Reed Switches collection includes options for different alarm systems, installation styles and entry-point protection needs.

Reasons to choose CTC Communications:

• Over 30 years of security industry experience
• Alarm accessories for homes and businesses
• Reed switches for doors, windows, shutters and commercial sites
• Australia-wide product delivery
• Professional installation available across Sydney
• Support for wired, wireless and hybrid alarm systems

Our Recommendation

For most homes, reed switches are worth considering on the main entry doors, sliding doors, garage access doors and selected ground-floor windows. For businesses, they are especially important on shopfront doors, rear doors, stockrooms, roller shutters and loading bay access points.

If you are building or renovating, plan reed switches early so cabling can be hidden neatly. If you are upgrading an existing alarm, surface mount or wireless reed switches may be a practical option depending on your system.

Frequently Asked Questions