Abstract: An improved inverter or "fluorescent battery pack" useful particularly in an emergency lighting system with both magnetic and electronic ballasts of both "rapid start" and "instant start" configurations, the present inverter is rapidly installable in emergency lighting systems which include fluorescent lighting fixtures operable with either magnetic ballasts which are typically "non-isolated" or electronic ballasts which are typically "isolated". The inverter circuitry of the invention is simply installable in the present emergency lighting system due to an effective disconnection of the ballasts with concurrent connection between the inverter and lamping, only two effective connections to the lamp thus being necessary with a resulting avoidance of wiring redundancy.