Editing Emergency light (section)

==Modern installations==
[[Image:Emergency light.JPG|thumb|A small emergency light]]
In the United States, modern emergency lighting is installed in virtually every commercial and high occupancy residential building.  The lights consist of one or more incandescent bulbs or one or more clusters of high-intensity [[light-emitting diode]]s (LED).  The emergency lighting heads have usually been either incandescent PAR 36 sealed beams or wedge base lamps, but LED illumination is increasingly common. All units have some sort of a device to focus and intensify the light they produce.  This can either be in the form of a plastic cover over the fixture, or a reflector placed behind the light source.  Most individual light sources can be rotated and aimed for where light is needed most in an emergency, such as toward [[fire exit]]s.  

Modern fixtures usually have a test button of some sort which simulates a power failure and causes the unit to switch on the lights and operate from battery power, even if the main power is still on.  Modern systems are operated with relatively low voltage, usually from 6-12 VDC.  This both reduces the size of the batteries required and reduces the load on the circuit to which the emergency light is wired.  Modern fixtures include a small [[transformer]] in the base of the fixture which steps-down the voltage from main current to the low voltage required by the lights.  Batteries are commonly made of lead-calcium, and can last for 10 years or more on continuous charge.  US fire safety codes require a minimum of 90 minutes on battery power during a power outage along the path of egress.