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Fire Protection Glossary - W-X-Y-Z

W - X - Y - Z

Walk Test. A feature that allows a single person to test a fire alarm system.

Waterflow Detector. A device which detects the flow of water in a deluge system.

Waterflow Switch. An assembly approved for the service and so constructed and installed that any flow of water from a sprinkler system equal to or greater than that from a single automatic sprinkler of the smallest orifice size installed on the system will result in activation of this switch and subsequently indicate an alarm condition.

WATS (Wide Area Telephone Service). Telephone Company service allowing reduced costs for certain telephone call arrangement; it can be in-WATS or 800-number service where calls can be placed from anywhere in the continental U.S. to the called party at no cost to the calling party, or out-WATS, a service whereby, for a flat-rate charge, dependant on the total duration of all such calls, a subscriber can make an unlimited number of calls within a prescribed area from a particular telephone terminal without the registration of individual call charges.

Wavelength. The distance between the peaks of a sinusoidal wave. All radiant energy can be described as a wave having a wavelength. Wavelength serves as the unit of measure for distinguishing between different parts of the spectrum. Wavelengths are measured in microns (uM), or Angstroms (Å). The concept of wavelength is extremely important in selecting the proper detector for a particular application. There is a precise interrelation between the wavelength of light being emitted from a flame and the combustion chemistry producing the flame. Specific subatomic, atomic, and molecular events yield radiant energy of specific wavelengths. For example, ultraviolet photons are emitted as the result of the complete loss of electrons or very large changes in electron energy levels. During combustion, molecules are violently torn apart by the chemical reactivity of oxygen, and electrons are released in the process, recombining at drastically lower energy levels, thus giving rise to ultraviolet rations. Visible radiation is generally the result of smaller changes in electron energy levels within the molecules of fuel, flame intermediates, and products of combustion. Infrared radiation comes from the vibration of molecules or parts of molecules when they are in the superheated state associated with combustion. Each chemical compound exhibits a group of wavelengths at which it is resonant. These wavelengths constitute the chemical's infrared spectrum, which is usually unique to that chemical. This interrelationship between wavelength and combustion chemistry affects the relative performance of various types of detectors with respect to various fires.

Wet Location. See Location, Wet.

Wireless Control Panel. A component that transmits/receives and processes wireless signals.

Wireless Initiating Device. Any initiating device that communicates with an associated control/receiving equipment by some kind of wireless transmission path.

Wireless Protection System. A system or a part of a system that can transmit and receive signals without the aid of wire. It may consist of any of the following components:

Wireless Repeater. A component used to relay signals between wireless receivers or wireless control panels, or both.

Wireless Radio Linker. A device that receives, verifies, and retransmits coded low power radio frequency alarm and supervisory signals generated by wireless smoke detectors and other wireless initiating devices.

NOTE: In section 3-13 of the 1996 edition of NFPA 72, the term "wireless" was replaced with "low power radio" to eliminate potential confusion with other transmission media such as optical fiber cables. In making this change, the committee overlooked updating these definitions.

Wireless Smoke Detector. A smoke detector which communicates with associated control / receiving equipment using radio transmission.
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Some information may be found within this web site that is reprinted with permission from one or more of the following: NFPA 70 National Electrical Code®,NFPA 72® National Fire Alarm Code®, & NFPA 101® Life Safety Code®, Copyright© NFPA, Quincy, MA 02269.

This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety.