When the Lighting Control Module closes a single zone's contact, the Normal Power feeds through to both the Normal Lighting loads as well as the ESRB/ESRN's Switched Input. Even though the Normal/Emergency Lighting is being powered from the Emergency Panel, it is still controlled by the zone contact and 0-10Vdc signal on the controller. See image below for a wiring schematic:
When the Lighting Control Module opens a single zone's contact, the Normal Power stops at the open contact, and does not feeds voltage through to either the Normal Lighting loads or the ESRB/ESRN's Switched Input. Even though the Normal/Emergency Lighting is being fed 0-10Vdc from the controller, the high voltage side of the load is broken by the ESRB/ESRN relay contact due to the lack of a control voltage on the Switched Input. See image below for a wiring schematic:
When there is no Normal Power present, the Lighting Control Module cannot control either the zone contact or the ESRB/ESRN. The ESRB/ESRN notices the absence of Normal Power. Therefore, they pass the Emergency Power through the relay contact and out to the Normal/Emergency Lighting. Because there is 0V coming out of the controller, and because there is high voltage applied to the power input of the Emergency Lighting loads, the Normal/Emergency Lighting loads come on at full brightness. See image below for a wiring schematic:
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