An electromagnetic door holder (electromagnetic door holder and release or hold-open device, sometimes informally called a mag hold open or electric doorstop) is a simple electromechanical mechanism which can be used to hold a fire door or security door open until given a signal to release. A fire alarm control panel or a similar emergency control system usually powers and controls the door holder.
A simple electromagnetic door holder consists of a strong electromagnet, usually attached to a wall or mounted in a floor pedestal enclosure, next to the door it controls. The mechanism may be mounted near the floor, at the upper corner of the open door, or at any convenient height along the latch edge (away from the hinged edge).
A steel plate, often mounted on a ball joint or swivel joint, is attached to the door so that it can contact the electromagnet when the door is fully opened. An electric current typically energizes the electromagnet to attract and hold the steel plate, keeping the door open. Unlike electromagnetic locks, the magnetic attraction of an electromagnetic door holder is usually weak enough that it can be manually overpowered at any time by anyone, allowing the door to close.[ citation needed ]
If a fire alarm control panel, burglar alarm control panel, or similar emergency system is triggered, it will cut electrical power to the electromagnetic door holders under its control. The door holders release, allowing the doors to close automatically using door closers. [1] [2] The electric power to keep the doors open is typically 12 VDC, 24 VDC (common), 24 VAC, 120 VAC, or 240 VAC.
The closed doors may or may not mechanically latch or lock in the closed position. Many fire doors do not lock, to allow building occupants to move within the building to find an exit easily. On the other hand, security doors may close, latch, and lock, to prevent passage. Other designs are used to secure sliding or overhead doors similarly, holding them open until a signal to release the doors to close automatically.
In life safety and security applications, electromagnetic door holders must be very reliable; the simplicity of the mechanisms helps considerably. They are designed to be fail-safe in that anything interfering with their operation (such as a power failure) will cause them to release the doors and allow them to close. [2]
To overcome possible remanent magnetism, which could cause the electromagnet to fail to release, some door holders are equipped with a spring-loaded pin that helps push the magnetic plate away from the electromagnet when the power is cut.
A door is a hinged or otherwise movable barrier that allows ingress (entry) into and egress (exit) from an enclosure. The created opening in the wall is a doorway or portal. A door's essential and primary purpose is to provide security by controlling access to the doorway (portal). Conventionally, it is a panel that fits into the doorway of a building, room, or vehicle. Doors are generally made of a material suited to the door's task. They are commonly attached by hinges, but can move by other means, such as slides or counterbalancing.
A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
In physical security and information security, access control (AC) is the selective restriction of access to a place or other resource, while access management describes the process. The act of accessing may mean consuming, entering, or using. Permission to access a resource is called authorization.
In engineering, a fail-safe is a design feature or practice that, in the event of a failure of the design feature, inherently responds in a way that will cause minimal or no harm to other equipment, to the environment or to people. Unlike inherent safety to a particular hazard, a system being "fail-safe" does not mean that failure is naturally inconsequential, but rather that the system's design prevents or mitigates unsafe consequences of the system's failure. If and when a "fail-safe" system fails, it remains at least as safe as it was before the failure. Since many types of failure are possible, failure mode and effects analysis is used to examine failure situations and recommend safety design and procedures.
A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by current in excess of that which the equipment can safely carry (overcurrent). Its basic function is to interrupt current flow to protect equipment and to prevent fire. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset to resume normal operation.
A crash bar is a type of door opening mechanism which allows users to open a door by pushing a bar. While originally conceived as a way to prevent crowd crushing in an emergency, crash bars are now used as the primary door opening mechanism in many commercial buildings.
Door furniture or door hardware refers to any of the items that are attached to a door or a drawer to enhance its functionality or appearance.
A security alarm is a system designed to detect intrusions, such as unauthorized entry, into a building or other areas, such as a home or school. Security alarms protect against burglary (theft) or property damage, as well as against intruders. Examples include personal systems, neighborhood security alerts, car alarms, and prison alarms.
A door closer is a mechanical device that regulates the speed and action of a door’s swing. Manual closers store the force used to open the door in some type of spring and reuse it to close the door. Automatic types use electricity to regulate door swing behavior.
An electric bell is a mechanical or electronic bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing, clanging or ringing sound. Electromechanical bells have been widely used at railroad crossings, in telephones, fire and burglar alarms, as school bells, doorbells, and alarms in industrial areas, since the late 1800s, but they are now being widely replaced with electronic sounders. An electric bell consists of one or more electromagnets, made of a coil of insulated wire around an iron bar, which attract an iron strip armature with a clapper.
A latch or catch is a type of mechanical fastener that joins two or more objects or surfaces while allowing for their regular separation. A latch typically engages another piece of hardware on the other mounting surface. Depending upon the type and design of the latch, this engaged bit of hardware may be known as a keeper or strike.
An electronic lock is a locking device which operates by means of electric current. Electric locks are sometimes stand-alone with an electronic control assembly mounted directly to the lock. Electric locks may be connected to an access control system, the advantages of which include: key control, where keys can be added and removed without re-keying the lock cylinder; fine access control, where time and place are factors; and transaction logging, where activity is recorded. Electronic locks can also be remotely monitored and controlled, both to lock and to unlock.
A fire alarm system is a building system designed to detect, alert occupants, and alert emergency forces of the presence of fire, smoke, carbon monoxide, or other fire-related emergencies. Fire alarm systems are required in most commercial buildings. They may include smoke detectors, heat detectors, and manual fire alarm activation devices. All components of a fire alarm system are connected to a fire alarm control panel. Fire alarm control panels are usually found in an electrical or panel room. Fire alarm systems generally use visual and audio signalization to warn the occupants of the building. Some fire alarm systems may also disable elevators, which are unsafe to use during a fire under most circumstances.
An electric strike is an access control device used for door frames. It replaces the fixed strike faceplate often used with a latch. Like a fixed strike plate, it normally presents a ramped or beveled surface to the locking latch allowing the door to close and latch just like a fixed strike would. However, an electric strike's ramped surface can, upon command, pivot out of the way when the lock on the door is in the locked position and the door is opened, allowing a user to pull/push the door to open it without operating the mechanical lock or using a mechanical key. After the door is opened past the keeper, the keeper returns to its standard position and re-locks when power is removed or applied, depending upon the strike's configuration.
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A car door is a type of door opening, typically hinged on its front edge, but sometimes attached by other mechanisms such as tracks, for entering and exiting a vehicle. Doors most often integrate side windows for visibility from inside the car and can be locked to secure the vehicle.
The term door security or door security gate may refer to any of a range of measures used to strengthen doors against door breaching, ram-raiding and lock picking, and prevent crimes such as burglary and home invasions. Door security is used in commercial and government buildings, as well as in residential settings.
Vandal-resistant switches are electrical switches designed to be installed in a location and application where they may be subject to abuse and attempts to damage them, as in the case of pedestrian crossing switches. Vandal-resistant switches located on devices that are outdoors must be able to withstand extreme temperatures, dust, rain, snow, and ice. Many vandal-resistant switches are intended to be operated by the general public, and must withstand heavy use and even abuse, such as attempts to damage the switch with metal tools. These switches must also resist dirt and moisture.
An electromagnetic lock, magnetic lock, or maglock is a locking device that consists of an electromagnet and an armature plate.
A lockset is the hardware and components that make up the locking or latching mechanism that can usually be found on a door or other hinged object but can also include sliding doors and dividers. The components of a lockset can include the door handles, latch bolt, dead bolt, face plate, strike plate, escutcheon, thumbturn, push button, turn button, and other trim. The lockset and associated hardware typically defines a door's function and how a user could access the two adjacent spaces defined by the opening associated with the lockset.