Potter Releasing Systems - Manual (Page 6)

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A) Beam Construction - Ceilings having solid nonstructural members projecting down from the ceiling surface
more than 4 in. and spaced more than 3 ft., center to center.
B) Girders - Girders support beams or joists and run at right angles to the beams or joists. When the top of girders
are within 4 in. of the ceiling, they are a factor in determining the number of detectors and are to be considered as
beams. When the top of the girder is more than 4 in. from the ceiling, it is not a factor in detector location. Check
Valve - A self-operating valve that is used to prevent reverse flow through any portion of the system.
Central Station - A supervising station that is listed for central station service.
Central Station Fire Alarm System - A system or group of systems in which the operations of circuits and
devices are transmitted automatically to, recorded in, maintained by, and supervised from a listed central station.
Class A Circuit - Class A refers to an arrangement of monitored initiating device, signaling line, or notification
appliance circuits, which would permit a single open or ground on the installation wiring of these circuits from
causing loss of the systems intended function.
Class B Circuit - Class B refers to an arrangement of monitored initiating device, signaling line, or notification
appliance circuits, which would permit a single open or ground on the installation wiring of these circuits to
cause loss of the systems intended function.
Combination Detector - A device that either responds to more than one fire phenomenon or employes more
than one operating principle to sense one of these phenomenon. Typical examples are combination smoke/heat
detectors or a combination rate of rise and fixed temperature heat detector.
Compatibility Listed - A specific listing process that applies only to two wire devices [such as smoke
detectors] designed to operate with certain control equipment.
Control Valve - A valve controlling flow to water-based fire protection systems. Control valves do not include
hose valves, inspector’s test valves, drain valves, trim valves for dry pipe, pre-action and deluge valves, check
valves, or relief valves.
Digital Alarm Communicator Receiver [DACR] - A system component that will accept and display signals
from digital alarm communicator transmitters [DACT] sent over public switched telephone network.
Digital Alarm Communicator System [DACS] - A system in which signals are transmitted from a digital
alarm communicator transmitter [DACT] located at the protected premises through the public switched
telephone network to a DACR.
Digital Alarm Communicator Transmitter [DACT] - A system component at the protected premises to
which initiating devices are connected. The DACT will seize the connected telephone line, dial a pre-selected
telephone number to connect to a DACR, and transmit signals indicating a status change of the initiating device.
Display - The visual representation of output data other than printed copy.
Dry Pipe Sprinkler System - A sprinkler system employing automatic sprinklers that are attached to a piping
system containing air or nitrogen under pressure, the release of which (as from the opening of a sprinkler)
permits the water pressure to open a valve known as a dry pipe valve, and the water then flows into the piping
system and out the opened sprinklers.
End Of Line Device - A device such as a resistor or diode placed at the end of a class B circuit to maintain supervision
End Of Line Relay - A device used to supervise power [usually for 4-wire smoke detectors] and installed
within or near the last device on an initiating circuit.
Evacuation - The withdrawal of occupants from a building. Note: Evacuation does not include relocation of
occupants within a building.