Frequently Used Terms

Abbreviations
AHO - See Automatic hold open
AC - See Alternating current
ADA - See Americans with disabilities act
AHJ - See Authority having jurisdiction
AMP - See Ampere
BC - See Backcheck
BF - See Barrier Free
C - See Common
CWF - See Cold weather fluid
DA - See Delayed action
DC - See Direct current
DPDT - See Double pole double throw
EL - See Fail safe
ELS - See Extended length spindle
EU - See Fail secure
F - See Fire rated
FS - See Fail safe
FSE - See Fail secure
G - See Ground
HO - See Hold open
LAP - Less All Parts
NC - See Normally closed
NFS - See Non-fail safe
NHO - See Non hold open
NO - See Normally open
RX - See Request to exit
SC - See Sealed Closer
SHO - See Selective hold-open
SPDT - See Single pole double throw
SPLO - See Special Layout
SPST - See Single pole single throw
V - See Volt

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

Automatic Hold Open [AHO or A]
Available on certain series of closers. Preset at the factory for a specific degree of hold open. The degree of hold-open cannot be changed, nor can the closer be made into a non-hold-open closer.

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

Americans with Disabilities Act [ADA]
A US federal law dealing with the 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 signaling 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, optional on some door closers, which cushions the opening swing of a door and prevents it from slamming into the stop or wall.

Backset
The distance of measurement between the center of a cross-bore or cylinder hole on the face of the door and the bolt edge of a door.

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
Refers to a floor closer or pivot where the pivot point is located within the dimension of the door, usually at the center-line of the thickness of a door.

Cold Weather Fluid [CWF]
An door or floor closer option that should be considered in installations where ground temperature is constantly below +15°F. May be used in temperatures as low as -35°F.

Common [C]
A terminal on a form-C relay or 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 [DA]
A function of a door closer which delays the closing of a door to allow for passage by a wheelchair. It typically permits a door to remain ajar (at approximately 70°) for up to 30 seconds.

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.

Extended Length Spindle [ELS]
Closer bodies can be ordered with spindle extensions in ½" increments to accommodate installation variations such as thresholds or terrazzo pans.

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

Fire Rated [F]
A designation for door hardware indicating that it is for use on openings with fire-rated doors.

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, EL]
A feature of a security device designed to release, for safety purposes, during a power loss, (also known as fail-unlocked, fail-safe or reverse action). The device requires power to be electrically locked.

Fail Secure [FSE, NFS, EU]
Referring to an electrically operated lock which in an unpowered state is locked. (also known as fail-locked, fail-secure 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 [G]
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 electromagnetic lock.

Hold Open [HO]
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).

Less All Parts [LAP]
A designation for door closers supplied with a closer body only, including no accessories or components.

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.

Non-Fail Safe
(See fail secure).

Non Hold-Open [NHO or N]
Indicates a door closer that is not equipped with any hold open feature.

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.

Offset Hung
Refers to a door closer or pivot where the pivot point of the door is offset from the surface of the door. Typical offset dimensions are ¾" or 1½".

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

Physically Handicapped [PH]
Refers to door closers that are preset with 5 pounds of opening force.

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.

Request to Exit [RX]
A monitor or switch that signals an authorized request to exit a protected area.

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

Sealed Closer [SC]
Where water contact may occur with a floor closer. It provides gasketing and a cover plate that are epoxied around the cement case with the floor closer inside. This option is only available for replacement closers when the cement case is also replaced.

Selective Hold Open [SHO]
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 either close or open a circuit.

Special Layout [SPLO]
Custom application door hardware designed for non-standard installations.

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.

Tri-Volt
A triple voltage option on some magnetic holders which allows multiple input voltages.

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

Volt [V]
Unit of measurement of electrical current.