How will an ELTS2 handle a delay in emergency power startup?

Scenario

ETC recommends ELTS2 cabinets be fed with a constant source of emergency power.

Imagine an ELTS2 fed with Normal power only. Normal power drops out, and the generator-fed Emergency power takes a few seconds to start up. How will the ELTS2 behave? Will it stay in Normal mode, or switch into Emergency mode?

Fix/Solution

1. ELTS2 will lose power when Normal power drops out.
2. The ELTS2 should boot on the application of Emergency power.
3. It will detect the lack of Normal power, and switch into Emergency mode.

Having said that, most local codes have a time limit for lights to come back on in a power-loss situation (often 10 seconds or less). If the Emergency power startup and subsequent ELTS2 booting combined take longer than that limit, you could be held liable for a code violation. A constant Emergency power source is always preferable to an alternative.