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What is Access Control?

In physical security, the term access control refers to the practice of restricting entrance to a property, a building, or a room to authorized persons. Physical access control can be achieved by a human (a guard, bouncer, or receptionist), through mechanical means such as locks and keys, or through technological means such as access control systems like the Cobra Controls Access Control System. 

Physical access control is a matter of who, where, and when. An access control system determines who is allowed to enter or exit, where they are allowed to exit or enter, and when they are allowed to enter or exit.  

Historically this was partially accomplished through keys and locks. When a door is locked only someone with a key can enter through the door depending on how the lock is configured. However . . . 

Mechanical locks and keys do not allow restriction of the key holder to specific times or dates.

Mechanical locks and keys do not provide records of the key used on any specific door and the keys can be easily copied or transferred to an unauthorized person.

When a mechanical key is lost or the key holder is no longer authorized to use the protected area, the locks must be re-keyed.

Electronic access control uses computers to solve the limitations of mechanical locks and keys. A wide range of credentials can be used to replace mechanical keys. 

The electronic access control system grants access based on the credential presented.

When access is granted, the door is unlocked for a predetermined time and the transaction is recorded.

When access is refused, the door remains locked and the attempted access is recorded.

The system will also monitor the door and alarm if the door is forced open or held open too long after being unlocked.

How does an Access Control System Operate?

When a credential (card, fob, fingerprint, etc.) is presented to a reader, the reader sends the credential’s information, usually a number, to a control panel / processor. The control panel compares the credential's number to an access control list, grants or denies the presented request, and sends a transaction log to a database. When access is denied based on the access control list, the door remains locked. If there is a match between the credential and the access control list, the control panel operates a relay that in turn unlocks the door. The control panel also ignores a door open signal to prevent an alarm. Often the reader provides feedback, such as a flashing red LED for an access denied and a flashing green LED for an access granted.

The above description illustrates a single factor transaction. Credentials can be passed around, thus subverting the access control list. For example, Alice has access rights to the server room but Bob does not. Alice either gives Bob her credential or Bob takes it; he now has access to the server room. To prevent this, two-factor authentication can be used. In a two factor transaction, the presented credential and a second factor are needed for access to be granted; another factor can be a PIN, a second credential, operator intervention, or a biometric input.

There are three types (factors) of authenticating information:

something the user knows, e.g. a password, pass-phrase or PIN

something the user has, such as smart card

something the user is, such as fingerprint, verified by biometric measurement

Passwords are a common means of verifying a user's identity before access is given to information systems. In addition, a fourth factor of authentication is now recognized: someone you know, where another person who knows you can provide a human element of authentication in situations where systems have been set up to allow for such scenarios. For example, a user may have their password, but have forgotten their smart card. In such a scenario, if the user is known to designated cohorts, the cohorts may provide their smart card and password in combination with the extant factor of the user in question and thus provide two factors for the user with missing credential, and three factors overall to allow access.

How does an Electromagnetic Lock Operate?

An electromagnetic lock, magnetic lock, or maglock is a locking device that consists of an electromagnet and an armature plate. By attaching the electromagnet to the door frame and the armature plate to the door, a current passing through the electromagnet attracts the armature plate, holding the door shut. Unlike an electric strike a magnetic lock has no interconnecting parts and is therefore not suitable for high security applications because it is possible to bypass the lock by disrupting the power supply. Nevertheless, the strength of today's magnetic locks compares well with that of conventional door locks and they cost less than conventional light bulbs to operate. Power supplies incorporating a trickle-charged lead-acid battery pack can be used to retain security for short-term power outages.


The principle behind an electromagnetic lock is the use of electromagnetism to lock a door when energized. The holding force should be collinear with the load, and the lock and armature plate should be face-to-face to achieve optimal operation.


The magnetic lock relies upon some of the basic concepts of electromagnetism. Essentially it consists of an electromagnet attracting a conductor with a force large enough to prevent the door from being opened. In a more detailed examination, the device makes use of the fact that a current through one or more loops of wire solenoid produces a magnetic field. This works in free space, but if the solenoid is wrapped around a ferromagnetic core such as soft iron the effect of the field is greatly amplified. This is because the internal magnetic domains of the material align with each other to greatly enhance the magnetic flux density.

Technical comparison

Magnetic locks possess a number of advantages over conventional locks and electric strikes. For example, their durability and quick operation can make them valuable in a high-traffic office environment where electronic authentication is necessary.


- Easy to install: Magnetic locks are generally easier to install than other locks since there are no interconnecting parts.

- Quick to operate: Magnetic locks unlock instantly when the power is cut, allowing for quick release in comparison to other locks.

- Sturdy: Magnetic locks may also suffer less damage from multiple blows than do conventional locks. If a magnetic lock is forced open with a crowbar, it will often do little or no damage to the door or lock.


- Requires continuous power: To remain locked, the magnetic lock requires a constant power source. The power drain of the lock is typically around 3 watts, far less than that of a conventional lightbulb (around 60 watts), but it may cause security concerns as the device will become unlocked if the power source is disrupted. By comparison, electric strikes can be designed to remain locked should the power source be disrupted. Nevertheless, this behaviour may actually be preferable in terms of fire safety.


The magnetic lock is suitable for both in-swing and out-swing doors. Brackets (L bracket, LZ bracket, U bracket) are used to adjust the space between the door and lock. The magnetic lock should always be installed on the inside (secure side) of the door. Most installations are surface mounted. For safety, magnetic lock, cables, and wires should be inserted in the door or be a flush mount. Installation is as simple as installing the header of the door frame for out-swinging doors or using a Z-bracket for in-swinging doors. It is important to make sure the armature plate and the electromagnet align as closely as possible to ensure efficient operation. Magnetic locks are almost always part of a complete electronic security system. Such a system may simply consist of an attached keycard reader or may be more complex, involving connection to a central computer that monitors the building's security. Whatever the choice of locking system, fire safety is an important consideration.

Other variations and improvements on the electromagnetic locks have been developed. The most remarkable is the shear lock, where the armature does not directly pull off the face, but the load is instead in shear, like a mechanical stop. The shear magnetic lock allows a door to swing in both directions, as opposed to the original (and now ubiquitous) direct pull type, which normally works either in an in-swing or out-swing configuration.

An improved 'shear' electromagnetic lock was patented on May 2, 1989, by Arthur, Richard and David Geringer of Security Door Controls, an access control hardware manufacturing firm. (Maglocks.com carries and supports the full product offering of SDC Security) The device outlined in their designs was the same in principle as the modern magnetic lock consisting of an electromagnet and an armature plate. The patent did not make any reference to the manufacturing methods of the electromagnet and detailed several variations on the design, including one that used a spring-loaded armature plate to bring the armature plate closer to the electromagnet. The patent expired on May 2, 2009.

Holding force

A magnetic lock has a metal plate surrounded by a coil of wire that can be magnetized. The number of coils determines the holding force which characterizes the lock:

- Micro Size: 300 lbf (1,300 N) holding force.

- Mini Size: 600 lbf (2,700 N) holding force

- Midi Size: 800 lbf (3,600 N) holding force

- Standard Size: 1,200 lbf (5,300 N) holding force.

The standard size electromagnetic lock is used as a gate lock.

Electrical Requirements

The power for an electromagnet lock is DC (Direct Current), around 6 W. The current is around 0.5 A when the power is 12 V DC. Generally, the specification of the electromagnet locks is dual voltages 12/24 V DC. Single voltage output can be required for 12 V DC or 24 V DC applications. The figure presents the relationship between voltage and holding force. When the current is fixed, voltage is proportional to power consumption.

Application modes

For safety purposes, electric locks can be designed to operate in one of two modes:

Fail-Safe – to protect people: The lock is released if power cuts off.

Fail-Secure – to protect property: The lock remains closed if power cuts off.

An electromagnet lock is normally used in Fail-Safe situations, so it must satisfy applicable fire regulations so as to be safe in emergency situations.

Magnetic Locks (maglocks) Versus Electric Strikes

Magnetic locks and electric strikes are electrical hardware devices used to maintain the security of a door opening. Both of these devices can be activated by a range of tools, including passcodes, biometric readers, keycards or buzzers. When comparing magnetic locks to electric strikes, consider factors such as intended function, security needs, safety egress and cost to help you choose between the two.


A magnetic lock, or maglock, consists of a large magnet that is installed along the top of a door frame. A metal plate, or armature plate, is fastened to the door so it lines up with the magnet.

When electrical power is supplied to the magnet, it creates a magnetic charge that keeps the magnet tightly pressed to the metal plate. This keeps the door securely locked until power is removed or interrupted.

An electric strike must be used along with some other form of locking device, such as a lockset or exit device (panic bar). Electrical power is supplied to the strike, which holds the lock bolt in place, keeping the door locked until the strike is activated by a buzzer, keycard or other device.


With a magnetic lock, the door is always locked from both sides of the opening. This makes maglocks a very secure option for areas that require high levels of security. Users must activate the lock with a keycard or other device when leaving and when entering. A handle or latchset is used to operate the door, but typically has no locking function.

Electric strikes provide security only for the exterior side of the door. Occupants can freely exit at anytime from inside the building simply by turning the knob or handle, or by depressing the pad on the exit device. From the outside, the door can only be unlocked with a keycard or other activating device, which signals the strike to release the lock bolt.


All electrical hardware can be described as either "fail-safe" or "fail-secure." Fail-safe hardware stays locked when power to the hardware is cut, keeping the building secure. Fail-secure hardware unlocks once power is cut, allowing for safe egress of occupants.

A magnetic lock is always fail-safe, and unlocks automatically if power is cut.

Electric strikes can typically be set to either of these two options using an integral switch. All fire-rated doors must be equipped with fail-safe hardware for safe egress at all times.


Because a magnetic lock is installed on the face of the door and frame, it can be installed relatively easily by most contractors and do-it-your owners. It is one of the most effective types of hardware for securing both sides of a door, and provides a great door of force to keep the door secure.

Electric strikes are usually similiarly priced to magnetic locks, making them an equally good choice for building managers on a budget. It is also easier in general to meet fire and life safety codes with an electric strike than with a maglock. An electric strike is much less likely to delay egress because it can be easily operated from the inside of the building.


Magnetic locks can pose a potential safety hazard in terms of slowing egress during an emergency. Because of the complexity of powering and installing electric strikes, they must be chosen carefully based on the type of lock they will be used with. If the wrong strike is chosen, the lock bolt won't fit securely inside.

Magnetic Lock Installation Instructions

Step 1

Fold the mounting template to make a 90-degree angle. Place this up against the door frame and the door, ensuring that door opens outwards from this position. The holes in the template indicate where the holes need to be drilled to attach the magnetic lock. Use a pencil to mark the spots on your door and frame.

Step 2

Drill the holes according to the marks made by the template. Different size holes in the template require different size drill bits. The largest hole should be found on the actual door, in the center, and should be roughly 0.315 inches.

Step 3

Attach the armature plate to the door. The armature plate is the thinner of the two plates included in your magnetic door kit. Drill 1/2-inch hole for the sexnut bolt in the opposite side of the door if you have a hollow metal or a solid metal door. This hole should be opposite the 0.315 inch hole indicated by the template. Place the sexnut bolt in the hole you just made, and then place the rubber and metal washers over the hole in the opposite side of the door. Use the guide pins to help hold the armature plate in place at the left and right sides. Screw in the main armature screw, which goes in the center of the armature plate, through the washers and into the door. The sexnut bolt holds the screw in place.

Step 4

Connect the magnet mounting plate to the door frame. Place the small mounting screws in the circular holes in the far right and left of the mounting plate. The spare circular holes on the outside are for the fixing screws from the magnet. Push the power cable through the oval shaped hole on the mounting plate before attaching the plate to the door frame. Screw the plate into the door frame.

Step 5

Attach the magnet using the two long fixing screws and an Allen wrench. Tighten the tips of the two fixing screws into the mounting plate to secure the lock. Connect the power to test the lock.

How Magnetic Locks Work


A magnetic lock, often referred to as a mag lock, consists of an electromagnet and an armature plate. The magnet is mounted inside of the door opening, which prevents tampering, while the plate is installed on the face of the door. When the magnet is connected to an electrical source, it produces a strong magnetic attraction that holds the magnet tight to the plate, effectively locking the door. The lock is typically powered using either the building's electrical system or a separate battery pack. Because a mag lock can only be used with DC power, a converter unit must be added when relying on building power. These locks are said to be "fail-safe," meaning that once the power goes out, the door will remain unlocked, allowing occupants to exit safely.

Electromagnetic Theory

Mag locks are based on the science of electromagnetism. Based on the principles of electromagnetism, when a current is run through a loop of wire, or solenoid, a magnetic force will be produced. This magnetic force is of sufficient strength to prevent the door from opening under a specified amount of pressure. To increase the strength of the magnetic force, multiple solenoids may be used, or they may be placed around a core made of iron. The magnetic effect of the solenoids not only produces its only force, but also amplifies the natural magnetism of the iron. Mag locks are rated based on the amount of force they are able to withstand without failing. For example, a 1,200 pound Mag Lock can withstand 1,200 pounds of force while still keeping the building secure.


One of the biggest advantages to using a mag lock is that it can't be picked or tampered with like a traditional lock cylinder. No keys are used, as the lock is generally tied into an electrical security system. These systems rely on one of four basic methods to operate the lock. They are often connected to a buzzer, which must be manually released by someone inside the building before the door will open. A mag lock may also be used with a keypad system, where occupants enter a numerical code to activate the lock and open the door. In many commercial settings, card readers are used with these locks, making it easy to deactivate a card in the event an employee is terminated or loses his/her key card. Finally, in high-security situations, the mag lock may be activated by scanners that read fingerprints, retinas, or facial features of an occupant before they are permitted to enter.

What is an Electric Strike? and How does an Electric Strike work?

An electric strike is a device that's installed on a door to allow access with an access control system or some other type of remote release system. The electric strike, unlike a magnetic lock doesn't actually secure the door. A door with an electric strike is being secured by the lockset or door handle. What the electric strike does is allow access to a secured door without the need for a key to unlock the lockset.

If you look at a normal door, you'll see three major parts that keep it secure. The first part is the lockset. The lockset consists of several parts but the 2 major parts are the handle and the latch. The handle is the part that you use to open a door. The latch is the piece that sticks out the side of the door. This is the piece that actually keeps the door locked and retracts whenever the handle is turned. The third part is the strike (or strike plate or door strike). What the strike does is provide an hole for the latch to rest in.

The strike looks like a metal plate with a hole in it. When the latch falls inside of the hole, it keeps the door from opening. What the electric strike does is replace this strike plate. When the electric strike is used, the side of the strike is cut out and has a hinged piece of metal. The piece of metal swings whenever the release system is activated. This allows you to open the door without unlocking the handle. So basically the electric strike has the same hole as the strike plate except that the electric strike hinges on the side to allow the latch to move out and allow the door to open.

There are several advantages to using electric strikes over other types of locks. However . . .

Not all doors can use door strikes. Some doors that do not have locksets cannot use a electric door strike since a lockset is required.

Locksets may need to be replaced to use a electric door strike. There are many different types of locksets with many different functions. The correct function for an electric strike would be one that stays locked from the outside (can be momentarily unlocked with a key but not permanently) and has no type of lock/unlock button on the inside. This function is called a "store room function". Other types such as locks that have a lock/unlock button on the inside would defeat the purpose of the strike.

Permanent damage is done to door frame. In order to install a door strike, part of the door frame must be cut out. This is not a problem unless you want to move the strike to another door. That would leave a large hole in the strike. Some manufacturers sell filler plates to cover up the hole but most of the time, the strike would just be left in the door and another would be purchased for another door.

Can be affected by air pressure. Inside of an electric strike are several moving parts and if the latch of the door pushes on the hinged plate of the door strike causing a binding effect, the electric strike will not unlock. You can tell when this happens whenever the access system is activated but the electric strike will not unlock unless you pull on the door. Essentially you are taking the pressure off of the strike allowing it to unlock. This pressure is caused in some buildings by the pressure from the air conditioning system. If you feel the air rush out with the door partially opened, that same air will be pushing out on the door causing the strike to bind.

So should you use an electric strike for your access control system? Well, it all depends. There are many different types of electronic locks and each lock has it's advantages and disadvantages. If you've got a high profile door; one where appearance is very important; you may want to skip a maglock and go with a electric strike or maybe an electrified mortise lock. If you want a higher security door; one where an access card and not a key can open... a magnetic lock may be the ticket.