The 500-1ka (formerly ACPS-2K) is a variac (variable transformer) based, 2000W AC adjustable power supply. The output voltage can be read from the meter mounted on the control panel of the unit. This meter has limited accuracy. For accurate readings, user must hook up a separate multimeter to the output of the unit. The unit can be used to power up a variety of QTH lamps of up to 2000W (nominal power). The cooling fan interlock circuit prevents the power to be delivered to the lamp, without the cooling fan plugged in. This protects the lamp from overheating. User can operate the cooling fan without power delivered to the lamp, by cranking the output voltage dial to zero (max CCW position), and turning the main switch on. This is to allow for lamp cooling for a few minutes after the lamp has been switched off.