Wednesday, July 16, 2008

Basics of Fire Alarm System

A fire alarm control panel, also referred to as a fire alarm panel or FACP, normally referred to as a panel within the active fire protection industry, is a central control device for detecting, reporting and acting on occurrences of fires within a building. There are three types of panels: coded panels, conventional panels, and addressable panels.
Coded panels:
Coded panels were the earliest type of central fire alarm control, and were made from the 1950s to the late 1970s. A coded panel is similar in many ways to a modern conventional panel (described below), except each zone was connected to its own code wheel (Ex: An alarm in zone 1 would sound code 1-2-4, while zone 2 would sound 1-2-5), which, depending on the way the panel was set up, would either do sets of four rounds of code until the initiating pull station was reset (similar to a coded pull station) or run continuosly until the panel itself was reset. Large panels could take up an entire wall in a mechanical room, with dozens of code wheels. Lists of codes had to be maintained, sometimes with copies being posted above certain pull stations (this setup is commonly seen in older wings of hospitals). Smaller panels could be set up in one of two ways. Most of the time, the panel would only have one zone, and therefore, only one code. Common one-zone codes were 4-4-0 and 17-0-0 (which is similar to the 120 bpm March Time setting found on modern panels). Alternatively, the panel could be made with no code wheels, using only what was called the gong relay. In large systems, this was primarily used to acommodate existing coded pull stations. However, it could also be used as its own zone, with the connected horns or bells sounding continuosly instead of in a particular code. These panels are not very common today, but can sometimes be found in older buildings such as those on college campuses or hospitals.
Conventional panel:
In a conventional panel, fire detection devices including, but not limited to smoke detectors, flame detectors, heat detectors and manual call points or manual pull stations are joined up with a number connected to each circuit. When a device on the circuit is activated, the panel recognizes an alarm on that circuit and could be set up to take a number of actions including directly calling the fire department via an alarm transportation system (ATS).
Addressable panel:An addressable panel is a more modern type of panel, and has greater flexibility than a conventional panel. An addressable panel has a number of loops, where a number of devices are able to be connected, each with its own address. There is no standard protocol as such, and thus a number of proprietary solutions exist. Loop devices have traditionally been able to have 99 or 100 devices connected, but more recent protocols allow many more. This is usually overcome by having multiple loops on one system.

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