What are they, and what are the rules?
Emergency power systems (Art. 700) are at the top of the hierarchy of backup power systems. Legally required standby systems, which fall under Art. 701, hold the No. 2 spot. Optional standby systems (Art. 702) are third in the pecking order. Basically, their level of importance corresponds to the order in which they appear in the NEC. A system is legally required when any government agency having