The Edwards EC2-OS is a two-wire photoelectric smoke detector. It detects smoke using the light-scattering principle. First, smoke enters the detector’s optical chamber. Then, particles scatter the chamber LED’s light onto the photodiode. As a result, the detector signals an alarm condition back through the two-wire loop. The EC2-OS works on conventional two-wire initiating circuits. In addition, it is compatible with Edwards S10A conventional fire alarm panels.