ENERGIZE: to apply power

EQUALIZER LINE: line from below the pool surface to the body of a skimmer, designed to prevent air being drawn into the filter when the water level drops below the skimmer inlet; operates automatically

FACE PIPING: piping, with all valves and fittings, used to connect the filter system together as a unit 

FAIL - LOCKED: (1) electric lock that requires power to unlock (2) also called fail secure

FAIL SAFE: see fail-unlocked

FAIL SECURE: see fail-locked 

FAIL - UNLOCKED: (1) electric lock that automatically unlocks with power interruption (2) also called fail safe

FEET OF HEAD: basic measurement of pressure or resistance in a hydraulic system, which is equivalent to the height of a column of water that would cause the same resistance

FIRE DOOR LATCH: latch that has a 1/4-inch throw and an anti-friction reactor

FORM C CONTACT: switch mechanism that contains three terminals (normally open, common, and normally closed)

FUSE: protective device, placed in a circuit as a safeguard, that contains a strip of easily melted metal; when the current flow becomes too great, the metal melts, thus breaking the circuit

GOLD: very soft ductile material that is noted for its resistance to corrosive metals; it is used primarily as a coating or plating

GROUND: conducting connection between an electrical circuit and the earth or other large conducting body, thus making a complete electrical circuit

GROUND, EARTH: portion of a circuit that is connected to a buried metallic object such as a grounding rod or water pipe

HORSEPOWER: work done per unit of time; 1 horsepower equals 33,000 foot-pounds of work per minute or approximately 746 watts; motors for pumps are rated in horsepower

INPUT VOLTAGE: designed power source requirement needed by equipment in order to operate properly

INRUSH: initial surge of current through a load when power is first applied; lamp loads, inductive motors, solenoids, and capacitive load types 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: (1) system of multiple doors with controlled interaction (2) also known as lighttraps, airtraps, mantraps, and sallyports

INTERMITTENT DUTY SOLENOID: solenoid designed to be energized for short periods; continuous operation may damage an intermittent duty solenoid

LIGHT EMITTING DIODE (LED): diode, solid-state device that gives off virtually heatless colored light when electric current is passed through it; LEDs are very efficient, long lasting and are often used for digital readouts and annunciators; common colors include red, green, and amber

LIGHTTRAP: see interlock

LINE CORD: cord, terminating in a plug at one end used to connect equipment or appliances to a power outlet

LINE DROP: voltage loss occurring between any two points in a power or transmission line; such loss is due to resistance, reactance, or leakage of the line

LINE SUPERVISION: electrical supervision of a wire run to detect tampering (a cut or shorted wire); usually requires a terminating element at end of monitored wire loop

LINE VOLTAGE: voltage existing in a main cable or circuit, such as at a wall outlet

LOAD: any device that consumes electrical power; the amount of power required for operation of a circuit or motion is obtained that moves the bolt

LOAD RATING: control specification outlining the type of load, minimum and maximum currents, and the voltage

LOCAL ALARM: visual or audible signaling device located at monitored door, window, or other opening

LOCK STATUS SENSOR (LSS): relay type to operate the LED with an SPDT switch to indicate low voltage and tampering of the lock face locally or to a remote monitoring location