A typical fire protection system consists of the devices in
the fire alarm, control panel, valve switches, strobe and horn
system, sprinkler system, and manual call points. Electricity
is the energy that activates and powers up these components. It
is easy to see if the system is supplied by electricity at the
moment by looking at the control panel LED lights. These lights
indicate whether any electricity is powering the system, and
this supply line is either AC-powered or DC-powered, in all
A word on AC and DC: AC-source or Alternating Current source is usually the electrical system of the particular building, while DC-source or Direct Current source is usually the back-up batteries. Fire alarm batteries are devised to be the back-up electrical source of a fire alarm system whenever the AC-source fails.
On the control panel, the DC power can be lit up with either one of 2 types of light: red or green light. A red light means that the batteries are being currently used to power the system. A green light means that the batteries are currently being charged.
The DC power source is not only limited as a back up energy source but smaller capacity DC batteries are also used to power other fire alarm devices such as the smoke and carbon monoxide detectors, and also the temperature or thermostat device. When any inspection is done on the fire alarm system, it is important to test the batteries and make sure they are still working and have sufficient power.
Fire alarm batteries should be checked at least twice a year, because there is a big risk if they fail to work during an actual fire. There have been fatalities resulting from the failure of alarm devices to work, all because of the batteries.
Some fire alarm units may give out an audio warning when there is a need to replace the batteries. But it is best not to wait for the warning to occur before replacing the batteries, as you cannot predict when a fire emergency may occur. Proper fire alarm inspection should minimize the risk.