Frequently Used Terms.

Adjustable Hold Open [AHO]
A door closer option which can be adjusted to hold a door open at different positions.

Alternating Current [AC] An electric current that reverses (alternates) its polarity regularly and continually. Also known as AC current.

Americans With Disabilities Act [ADA]
A US federal law dealing with minimum standards of building accessibility, as well as other issues concerning individuals with disabilities.

Ampere [AMP]
The unit of measurement for the rate of current flow.

Annunciator
A signalling device which can be either audible or visual.

Audit trail
A running history of events which occur in an access control system.

Authority Having Jurisdiction [AHJ]
The person, usually within a municipality, charged with the application and interpretation of local life safety codes.

Backcheck [BC]
A hydraulic function built into a door closer which prevents a door from swinging open uncontrolled.

Backset
The distance of measurement between the center of a cross-bore and the bolt edge of a door or drawer.

Barrier Free [BF]
Having to do with the absence of restrictions to access by the handicapped.

Battery Backup
A backup source of power for an access control system.

Center Hung
A door hung on pivots, with the pivot point within the dimension of the door.

Common [C]
A terminal on a form-C relay or a single pole double throw switch which is used to complete a circuit.

Continuous Duty
The duty rating of an electrical device. Continuous duty rated devices are designed to be powered continually.
Current
The flow of electrons measured in amperes (amps).

Current Draw
The amount of current (amps) consumed by a device in an electrical circuit.

Delayed Action
A function of a door closer which delays the closing of a door to allow for passage by a wheelchair.

Delayed Egress
A means of egress controlled (delayed) to prevent pilferage. Delayed egress must meet the requirements of NFPA101.

Direct Current [DC]
An electric current that travels in only one direction and typically has a negative and positive polarity.

Double Acting (door)
A door which swings in both directions

Double Pole - Double Throw [DPDT]
A type of switch or relay (form-C) where two circuits are activated simultaneously.

Dry Contact
Terminals on a relay which do not supply power but function to open or close a circuit.

Exit Door
A door typically used as a means of egress in an emergency.

Face
The exposed part of a frame parallel to the surface of the wall.

Face (Door)
The surface of a door, parallel with the face of the door frame.

Fail Safe [FS]
A feature of a security device designed to release, for safety purposes, during a power loss, (also known as fail-unlocked or reverse action).

Fail Secure [FSE, NFS]
A type of electrically operated lock which in an unpowered state is locked. (also known as fail-locked or non-fail safe).

Field Selectable
An option which can be configured after manufacture, generally as the product is being installed.

Finish
The finished color of a lock or other door hardware.
Fire Door
A door constructed to provide a specific degree of fire protection. It is typically rated for a period of time as resistant to penetration by fire.

Form-C
A type of switch mechanism which includes three terminals: common, normally open and normally closed.

Ground
A conducting connection between an electric circuit and the earth.

Hand
The orientation of a locking device which matches the bevel or direction or swing of a door. Designations for handing are: RH, LH, RHR, LHR. On pairs of doors, the suffix -A may indicate that a leaf is the active leaf in the pair (i.e.: RHR-A).

Header
The horizontal member of a door frame above the door.

Holding Force
The bond strength of an electro-magnetic lock.

Hold Open
A door closer option which allows a door to be held open.

Inrush Current
The measurement of amperage that an electrical device needs when power is first applied.

Intermittent Duty
The duty rating of an electrical device which is not designed to be continuously powered.

Labeled Fire Door
(See fire door).

Load
(See current draw).

Maintained Contact Switch
A switch designed to continually pass current or close a circuit in its normal condition.

Momentary Contact Switch
A switch designed to pass current or close a circuit on demand.

Monitoring
A method of indicating the operational status or security condition of a locking device or a door.

NFPA 101
National Fire Protection Association life safety code.

Normally Open [NO]
The normal condition of a switch or relay contact in which a circuit is open.
Normally Closed [NC]
The normal condition of a switch or relay contact in which a circuit is closed.

No Special Knowledge
A descriptive term which relates to the NFPA101 life safety code.

Non-Fail Safe
(See fail secure).

Operating Current
The measurement of amperage that an electrical device needs after the device has been initially powered.

Rail
One of the horizontal members of a door.

Rectifier
An electrical device which allows current to flow in one direction only. It converts AC current to DC.

Reveal
The distance between the face of a door frame and the face of a door.

Selective Hold Open
A door closer option which allows a door to be held open and can be enabled or disabled on demand.

Silent Operation
The quiet operational mode of a locking device which typically buzzes or makes other noise when energized.

Single Acting (Door)
A door which swings in only one direction.

Single Pole Double Throw [SPDT]
The description of a form-C contact.

Single Pole Single Throw [SPST]
A switch with only two terminals which close or open a circuit.

Stile
The vertical member of a door to which a locking device is installed.

Stop
The part of a door frame against which the door closes.

Time Delay
A pre-set period of time when a circuit is either open or closed in order to activate a locking device.

UL listed
A listing in the UL directory for a device which has passed specific Underwriters Laboratories tests.

Volt [V]
The unit of measurement of current.