2006 New York Code - Power Source.

 
    §  27-382  Power source. (a) Where a total of more than four lights is
  required, exit lighting shall be connected to an emergency power  source
  or  to  storage  battery  equipment  meeting  the  requirements  of  the
  commissioner, provided, however, that in existing  buildings,  the  exit
  lighting  may be on circuits that are separate from the general lighting
  and power circuits, taken off ahead of the main switch.
    (b) Existing high rise buildings classified in occupancy group C, D or
  H and existing buildings classified in  occupancy  group  E,  G  or  J-1
  (except  for  "residential  hotels,"  as  such  term  is  defined by the
  commissioner pursuant to rules and regulations) shall  comply  with  the
  requirements  of this section on or before April first, nineteen hundred
  eighty-seven.