Fire Detection sensors Systems

Fire detection sensors are available in two categories called heat detectors
and smoke detectors. They operate on a principle of detecting heat rise or
smoke in the home and can be either hard-wired with voltage supplied by the
AC power wiring or battery operated. Most fire detectors currently available
are powered by 9-volt DC transistor radio batteries, 120-volt AC power
wiring, or 120-volt AC power with battery backup. Wired-in smoke detectors 

connected to a fire or security system are usually powered by DC from
the security panel. This gives the detectors a natural battery backup in the
event of a power failure. Common voltages are 6v, 12v, and 24v DC with 12v
DC being the most common.

Some 120v AC units have the capability to interconnect so that when one
unit activates, it causes the audible alarm in the other units to sound. Units
can also be purchased that have a relay output for connection to any security 

system control panel or wireless transmitter. The most common types
available in hardware stores operate as independent sensors that are battery
powered, are not connected to the security system, and have their own audible 

alarm sounder. Heat sensors operate using a different technology from
smoke detectors. The basic design features of each type are summarized in
the following paragraph.