alternating current (AC) - An electric current that reverses its direction regularly and continually. The voltage alternates its polarity and direction of current flow from negative to positive.

American National Standards Institute (ANSI) - A federation of trade, technical and professional organizations, government agencies and consumer groups that coordinates standards development, publishes standards, and operates a voluntary certification program.

American Society for Testing Materials (ASTM) - An organization that tests materials and attempts to set standards on various materials for industry.

American Wire Gauge (AWG) - The standard system in the United States for designating wire size (diameter of metal).

ampere (amp) - Unit of measurement for the rate of electrical current flow characterized by the symbols "I" (in ohm's law formulas) or "A". One ampere is the current flowing through one ohm of resistance at one volt potential.

ampere/hour (AH) - Measurement of a battery's capacity. One ampere of current flowing for one hour equals one ampere/hour.

annunciator - Audible and visual signaling device.

authorized release device - A device that when activated allows authorized persons to enter or exit monitored and controlled openings without triggering alarm. The authorized release may be a keyed switch, card reader, digital code reader and so forth.

battery standby - A means of automatically switching over to stored battery power during local primary power failure.

break - To open an electrical circuit.

brownout - Low line voltage which can cause mis-operation of and possible damage to equipment. For example, a motor started at low voltage can actually be in a lock-rotor condition and overheat.

cam - A rotating eccentric piece attached to the end of a cylinder plug to actuate a lock or latch mechanism.

circuit - Path through which electrical energy flows.

circuit closed - (1) An electrical circuit in which current normally flows until interrupted by the opening of a switch or a switch-type electronic component. (2) A circuit or switch in which the contacts are closed during normal operation.

closure - The point at which two contacts meet to complete a circuit.

coil, electric - Successive turns of insulated wire that create a magnetic field when an electric current is passed through them.

conductor - Material with the ability to carry electric current. The term is also used for an electric wire.

conduit - A tube or trough for protecting wires or cables. It may be a solid or flexible tube in which
insulated electrical wires are run.

connector - Generally, any device used to provide rapid connect/disconnect service for electrical cable and wire terminations.

contacts - Electrically conductive points, or cell points, used to make or break an electrical circuit mechanically.

continuous duty - Refers to a device that can operate continuously with no off or rest periods.

current - The flow of electrons through an electrical conductor. Current is measured in amperes (A).

deadbolt - A bolt operated manually and not actuated by springs. When locked, the bolt cannot be forced back. A deadbolt is operated (projected and retracted) by a key cylinder or lever handle.

deadlatch - A latch in which the latchbolt is positively held in the projected position by an auxiliary mechanism.

decibel (dB) - A unit of measurement used to compare measured levels of sound energy (intensity) to the apparent level detected by the human ear, expressed as a logarithmic ratio.

de-energize - To remove power.

delay - A period of time before or during an event.

delay on break - A term used to describe a mode of operation relative to timing devices. The delay begins when the initiate switch is opened (delay break of initiate switch).

delay on energization - A term used to describe operation relative to timing devices. The delay begins when the initiate switch is closed for application of power to the input.

direct current (DC) - Electrical current that travels in only one direction and has negative and positive polarity. It may or may not have an AC ripple component. DC sources that are unfiltered should be referred to as full-wave or half-wave rectified AC.

dogging device - As used in exit devices, a mechanism that fastens the cross bar in the fully depressed position, and also retains the latch bolt or bolts in a retracted position, thus permitting free operation of the door from either side.

door status switch (DSS) - A DSS is a switch used to monitor whether a door is in an opened or closed position.

double pole, double throw (DPDT) - A term to describe a switch or relay output contact form (2 form C) in which two separate switches (with a normally open and normally closed contact and a common connection) operate simultaneously. This form is used to make and break two separate circuits.

dry contact - Metallic points making (shorting) or breaking (opening) a circuit. The switched circuit must have its own source of power and is merely routed through the dry contacts.

energize - To apply power.

fail locked - Refers to an electric lock that requires power to unlock. Also called fail secure.

fail unlocked - Refers to an electric lock that automatically unlocks with any power interruption. Also called fail safe.

form C contact - A switch mechanism that contains three terminals (normally open, common, and normally closed).

fuse - A protective device, placed in a circuit as a safeguard, that contains a metal filament. When the current flow becomes too great, the metal melts, thus breaking the circuit.

gold - A very soft, ductile material that is noted for its resistance to corrosive media. It is used primarily as a coding or plating.

ground - A conducting connection between an electrical circuit and the earth or other large conducting body to serve as an electrical ground, thus making a complete electrical circuit.

ground, earth - The portion of a circuit that is connected to a buried metallic object, such as a grounding rod or water pipe.

input voltage - The designed power source requirement needed by equipment in order to operate properly.

inrush - The initial surge of current through a load when power is first applied. Lamp loads, inductive motors, solenoids, and capacitive loads all have inrush or surge currents higher than the normal running or steady state currents. Resistive loads, such as heater elements, have no inrush.

interlock - A system of multiple doors with controlled interaction. lnterlocks are also known as lighttraps, airtraps, mantraps, and sallyports. (See security interlock).

intermittent duty solenoid - A solenoid designed to be energized for short periods of time. Continuous operation may damage an intermittent duty solenoid.

latch - The locking of a circuit by means of a holding contact.

light-emitting diode - A diode, a solid-state device, that gives off virtually heatless colored light when electric current is passed through it. LEDs are very efficient and long-lasting and are often used for digital readouts and annuciators. Common colors include red, green, and amber.

line drop (line loss) - A voltage loss occurring between any two points in a power or transmission line. Such loss, or drop, is due to the resistance, reactance, or leakage of the line.

line voltage - The voltage existing in a main cable or circuit, such as at a wall outlet.

listed - Refers to equipment or materials included in a list published by an authorizing organization. The listing states that the equipment or material met appropriate standards or has been tested for and
suited to a specific application.

load - Any device that consumes electrical power; the amount of power required for operation of circuit or device.

load rating - A control specification outlining the type of load, the minimum (min.) and the maximum (max.) currents, and the voltage.

local alarm - A visual or audible signaling device at a monitored door, window, or other opening.

lock status sensor (LSS) - Indicates low voltage and/or tampering of the lock face locally or at a remote monitoring location through a relay and LED.

maintained contact switch - A switch that, when activated, maintains that position until it is deactivated.

maximum rating - The absolute maximum condition in which a device is designed to operate. Voltage frequency, current, temperature, humidity, shock and other parameters can be specified as maximum.

mode of operation - The specified operating condition of a switch, lock door system, and so forth.

momentary duty lock - An electric lock equipped with a solenoid that is energized only momentarily.

momentary switch - A spring-loaded contact that, when pressed, activates the contacts. When pressure is removed, the contacts revert to normal.

mother board - A master printed circuit board used to interface the activities of individual printed circuit boards and the devices being controlled/monitored. The mother board is usually located on the back of a control panel assembly; individual printed circuit boards often plug into it.

National Electrical Code (NEC) - A consensus standard published by the National Fire Protection Association (NFPA); commonly called "code."

National Electrical Manufacturers Association (NEMA) - An organization that is know for its standardization of wire and cable specifications.

noise - The unwanted and/or unintelligible signals picked up on a cable circuit.

normally closed (NC) - The condition or position of contact prior to initiation or energization, in this case, a closed condition.

normally open (NO) - The condition or position of a contact prior to initiation or energization, in this case, an open condition.

operating voltage - The voltage by which a system operates; a nominal voltage with a specified tolerance applied; the design voltage range necessary to remain within the operating tolerance. For example, for a system specified 120 volts +/- 10 percent of nominal, 120 volts is the nominal voltage and design voltage range is 108 to 132 volts AC.

output voltage - The designed power source produced by a power supply to operate equipment.

potentiometer (pot) - Variable resistor.

primary - The transformer winding that receives energy from a supply circuit.

printed circuit board - A means of making electrical interconnections without using insulated wires. Printed circuit boards provide a supporting and insulating medium for components and conductors in a form that is readily adaptable to mat assembly.

rated voltage - The maximum voltage at which electric components can operate for extended periods without undue degradation or safety hazard.

rectifier - A solid-state electrical device that allows current to flow in one direction only. It is designed to convert alternating current to direct current.

recycle time - The time needed to reset and reinstate the timing function and remain within the specified timing tolerances. Recycle time is generally specified "during timing" or "after timing".

regulated power supply - Provides a constant output, regardless of voltage variations.

relay - An electrically controlled device that opens and closes electrical contacts to affect the operation of other devices in the same or another electrical circuit.

remote alarm - A visual or audible signaling device used to signal violations at locations removed from the central control station or monitored opening. For example, a remote alarm may be placed on the roof, in a stair tower, or at guard stations outside of a building.

remote reset - A switch located at a monitored opening. If a violation occurs, the alarm at the control console cannot be turned off until the door is secured and the remote reset is activated. Its purpose is to ensure the inspection of an opening that has been violated or left open.

reset time - The time required to return the output to its original condition.

resistance - The opposition to the flow of an electric current (measured in ohms); the reciprocal of conductance.

resistor - A circuit element whose chief purpose is to oppose the flow of current.

secondary - The transformer winding that receives energy by electromagnetic induction from primary.

security condition sensor (SCS) - A sensitive crystal relay that operates the LED and an SPDT switch, which indicates low voltage and tampering of the lock locally or to a remote monitoring location. Primarily used in higher security applications.

security interlock - A multi-door system in which doors are normally closed and locked; releasing door disables the releases for all other doors until the first door is closed and relocked.

short - An improper connection between current-carrying wire and neutral or ground.

single poIe, double throw (SPDT) - A term used to describe a switch or relay contact form (1 form C), that has a normally open and a normally closed contact with a common connection.

single poIe, single throw (SPST) - A switch with one moving and one stationary contact, available either normally open (NO) or normally closed (NC).

solenoid - An electromechanical device that operates the Iockbolt. When electricity is applied, a mechanical motion is obtained that moves the bolt.

spike - A momentary increase in electrical current. Spikes can damage electronic equipment.

springlatch - A beveled latchbolt that is activated by springs.

strike - A plate mortised into or mounted on the door jamb to accept and restrain bolt when the door is closed. In some metal installations of deadlock, the strike may simply be an opening into the jamb. (Synonym: keeper)

switches - Devices that make or break connections in an electrical or electronic circuit. In computing systems, they are also used to make selections. (The toggle switch, for example, completes a condition jump.) Switches are usually manually operated but can also work by mechanical, thermal, electromechanical, barometric, hydraulic, or gravitational means.

switch, normally open - A switch that, when not activated, is open and does not permit current flow.

switch, normally closed - A switch that, when not activated, is closed to form a path for current.

transformer - An electric device that changes voltage in direct proportion to currents and in inverse proportion to the ratio of the number of turns of primary and secondary windings. The input side of transformer is the primary side. The output low-voltage side is called the transformer secondary.

transient - Any increase or decrease in the excursion of voltage, current, power, heat, and so forth, above or below a nominal value that is not normal to the source. (See transient voltage.)

volt (V) - A unit of electromotive force. It is the difference of potential required to make a current of one ampere through a resistance of one ohm.

voltage - The term most often used (in place of electromotive force, potential, potential difference or voltage drop) to designate electrical pressure that exists between two points and is capable of producing a flow of current (when a closed circuit is connected between the two points).

voltage drop - Voltage loss experienced by electric circuits due to two principal factors: (1) wire size and (2) length of wire runs.

volt/amp (VA) rating - The product of rated input voltage multiplied by the rated current. This establishes "apparent energy" available to accomplish work.

watt - The common unit of electrical power. A watt is dissipated by a resistance of one ohm through which one ampere flows.

zone - A specific area of protection; a portion of a large protected area.