An electromagnetic lock is one of the most widely used locking mechanisms in access control systems. Its job is to hold the door shut with magnetic force and release it only once the access control system approves entry.
Unlike the other components in the system, the lock is mounted on the door itself and becomes an inseparable part of the locking mechanism. Choosing it well affects your security level, the reliability of the system, how well it suits the door type, and how the installation is carried out.
It is also the component users feel most directly. A door that unlocks a beat late, a lock that clunks on every release, or a door that never quite closes becomes a daily complaint even when everything else in the system works exactly as designed.
In this guide, we explain how an electromagnetic lock works, how it fits into an access control system, what to check before choosing one, and how to pick the right solution for a project.
What Is an Electromagnetic Lock?
An electromagnetic lock is a locking mechanism based on magnetic force. It has two main parts: a magnet unit, usually mounted on the frame, and a steel armature plate mounted on the door.
When the lock is energized, a strong magnetic field holds the armature plate against the magnet unit and the door is locked.
When the access control system approves entry, the controller cuts power to the lock for a few seconds, the magnetic force releases, and the door can be opened.
The lock itself has no moving parts. There is no bolt travelling in and out and no motor, which is where both its reliability and the quietness of its operation come from.
How Does an Electromagnetic Lock Connect to the Access Control System?
The electromagnetic lock connects over dedicated cabling to the power supply and to the access control system’s controller.
When an employee or visitor identifies with a card, a phone, or another credential, the controller checks the permission. If entry is approved, it cuts power to the lock for the period configured in the system and the door can be opened.
In many cases a door position sensor and a request-to-exit button are wired in as well, letting the system know whether the door is open or closed and allowing convenient egress from inside the building.
The door position sensor is what turns locking into information. Without it, the system knows only that it sent a release command — not whether the door actually opened, whether it closed again afterwards, or whether it was propped open. With one, the controller can raise an alert on a door held open or a door forced without a valid permission.
Want the full picture? Read the complete guide to choosing an access control system →
Fail-Safe vs. Fail-Secure: How the Door Behaves With No Power
This is the most important distinction to understand before choosing any locking mechanism, and it says nothing about the quality of the lock — only about how it behaves when things fail.
An electromagnetic lock is fail-safe: it locks as long as it is energized, so cutting power releases it and the door opens. That behaviour is deliberate, and it is what ensures people can leave the building during a power cut or a system fault.
Electric strikes and other electric locks also exist in a fail-secure version, which stays locked with no power.
Two practical conclusions follow. First, when a door must stay locked through a power cut — a server room or a stockroom, for instance — a maglock alone is not the answer, and it needs either a power supply with battery backup or a different locking mechanism. Second, even with battery backup fitted, its purpose is continuity of operation rather than removing free egress: the exit path has to stay open under every condition.
Egress and Fire Safety
In any electromagnetic lock installation, how people get out matters exactly as much as how they get in.
A complete installation usually combines three complementary mechanisms:
- A request-to-exit button on the inside, which releases the door for everyday egress and reports it to the controller.
- An emergency release on the exit side, which cuts power to the lock directly, independent of the controller or the software being healthy.
- A connection to the fire alarm system, which releases every door for free egress the moment the alarm triggers. On EntryBit controllers this is a dedicated fire-alarm interface (FAI) input, acting at the hardware level.
That combination is what lets a door be locked from outside and open from inside at the same time. The exact requirements depend on the building type, the escape routes, and the codes that apply to it, so settle them with the project’s safety consultant at design time rather than at the end of the installation.
Want to see how this is implemented in the controller? Meet the EntryBit access controllers →
How Much Holding Force Does an Electromagnetic Lock Provide?
One of the most important figures when choosing an electromagnetic lock is its holding force.
Holding force represents the force required to separate the magnet from the armature plate while the lock is energized, and it is usually quoted in kilograms.
Among the common models you will find:
- 280 kg, generally suited to interior doors, offices, and low-traffic entrances.
- 350 kg, one of the most common models, suited to most entrance doors in offices, public buildings, and businesses.
- 500 kg and above, intended for heavier doors, gates, or areas that require a particularly high level of security.
Choosing the holding force is not based on door weight alone, but also on the door type, how often it is used, the installation conditions, and the level of security required.
Keep in mind that the quoted holding force is only achieved when the armature plate meets the magnet fully and squarely. A door out of alignment, a plate installed with a gap, or a hinge that has loosened over time all reduce the force in practice — which is why a door that gives way to a shove usually points to installation or alignment rather than to a lock that is too weak.
Which Doors Suit an Electromagnetic Lock?
Electromagnetic locks suit a wide range of doors, including glass, aluminium, metal, and timber.
They are especially common in offices, office buildings, clinics, schools, public buildings, and businesses where entry needs to be controlled through an access control system.
The installation method varies with the door type, the swing direction, and the frame. An inward-opening door usually allows the lock to be mounted directly on the frame, while an outward-opening door calls for Z and L brackets. Glass doors have dedicated brackets that attach to the door without drilling the glass itself.
Brackets are not a minor detail. They determine whether the lock reaches its full holding force, so make sure the right bracket is specified and ordered with the lock rather than improvised on site.
Power Supply, Wiring, and Backup
An electromagnetic lock draws current continuously: it holds power for as long as the door is locked, which is nearly always.
Check that the power supply matches the lock’s operating voltage and the current it draws, and size it against every load on the system together rather than door by door. Where the lock sits far from the controller, account for voltage drop along the cable run as well; otherwise it shows up as holding force below what the datasheet promises.
Two more details worth confirming with the installer:
- Battery backup, where continuity of operation through a power cut is required.
- Back-EMF suppression when the lock is de-energized. An electromagnetic lock is an inductive load, and switching it off generates a reverse voltage spike that can damage relay contacts and disturb other components. A suppression component across the lock prevents it.
The Advantages of an Electromagnetic Lock
Electromagnetic locks are considered a reliable solution and relatively simple to install, which is why they are so widely used in access control systems.
Among their main advantages:
- High reliability.
- Fast, quiet operation.
- Compatibility with a wide range of door types.
- Straightforward integration with access control systems.
- Relatively low maintenance, with no moving parts.
- Suitability for high-frequency use.
- Free egress built in during a power cut.
When Is a Different Locking Mechanism the Better Choice?
An electromagnetic lock is not the right answer for every door, and it pays to know that at design time.
- When the door has to stay locked through a power cut, and it is not on an escape route.
- When the door needs to be mechanically latched into the frame — an exterior door exposed to wind, for example.
- When there is no frame or structure that allows the magnet unit and the plate to sit squarely opposite each other.
- When the door needs to be secured at several points along its height, as with unusually tall or heavy doors.
In each of those cases an electric strike, a dedicated electric lock, or a motorized lock is usually the better fit, depending on the door and the requirements.
What to Check Before Choosing an Electromagnetic Lock
Before choosing a lock, it is worth checking several important parameters:
- What holding force is required.
- Whether the lock suits the door type and its swing direction.
- Whether it is rated for indoor or outdoor installation.
- Its operating voltage and the current it draws.
- Whether it matches the system’s power supply, including the total of every load.
- Whether the right brackets exist for that door type.
- Whether the lock provides a status output, so the controller can confirm it is genuinely locked.
- What the egress path looks like: request-to-exit button, emergency release, and the fire alarm connection.
Choosing the lock well at design time makes for a simpler installation and reliable operation for years.
Summary
An electromagnetic lock is one of the most widely used locking mechanisms in access control systems. It works through magnetic force, integrates fully with the access control system, and gives you control over the door according to the permissions you defined.
When choosing one, consider the holding force, the door type, the installation conditions, how the door behaves with no power, and how egress from the building is handled.
Getting the lock, the controller, the power supply, and the door to match is what lets the system run reliably, safely, and comfortably for years.
Choosing the reader for the same door? Read the guide to choosing an access control reader →
Frequently asked questions
What happens to an electromagnetic lock during a power cut?
An electromagnetic lock holds the door with power, so with no power it releases and the door opens. That fail-safe behaviour is deliberate and is what guarantees free egress. When a door must stay locked through a power cut, it needs a power supply with battery backup or a different locking mechanism.
How much holding force do I need?
280 kg generally suits interior doors and low-traffic entrances, 350 kg is the common choice for most office and public-building entrance doors, and 500 kg or more is intended for heavy doors, gates, and areas that require a high level of security. The choice also depends on the door type, how often it is used, and the installation conditions.
Does an electromagnetic lock work on a glass door?
Yes. Glass doors use dedicated brackets that attach to the door without drilling the glass itself, and aluminium doors use Z and L brackets depending on the swing direction and the frame.
Does the lock block people from getting out of the building?
No. Egress must stay possible at all times, so the installation includes a request-to-exit button and, in many cases, an emergency release and a connection to the fire alarm system that releases the doors when the alarm triggers. Confirm the exact requirements with the project's safety consultant.
What is the difference between an electromagnetic lock and an electric strike?
An electromagnetic lock holds the door with magnetic force and is fail-safe: no power means released. An electric strike is fitted in the frame and releases only when the door is opened, and it also exists in a fail-secure version that stays locked during a power cut. Choosing between them depends on the door and on how it must behave when there is no power.