Emergency Lighting Transfer System. A Listed device that transfers a branch circuit from the output of a dimmer to a constant emergency power source in the event of an emergency power outage. Sometimes referred to as a BATS or Branch Circuit Automatic Transfer Switch. An ELTS must be a true "Automatic Transfer Switch" (ATS) and must meet the stringent requirements of the UL1008 standard. Sometimes confused with the ATS is the Automatic Load Control Relay (ALCR), another device used in Emergency Systems. The Automatic Load Control Relay (LCR) is used for bypassing a dimmer or wall-switch, and cannot be used for transferring a load between normal and emergency power sources. It is listed to the UL924 standard, a much less stringent document. For more details, see the article Understanding Control of Emergency Lighting Circuits by Steve Terry from 2004. View attachment Understanding Control of Emergency Lighting Circuits.pdf See also the article Understanding Control of Emergency Lighting Circuits—2010 Update by Steve Terry, Mitch Hefter, and Ken Vannice that appeared in the Spring 2010 issue of ESTA's Protocol magazine. View attachment Protocol_3-10.pdf One system of the type discussed is Union Connector: Emergency Transfer Systems. Another is ETC's ELTS2.