Satco has a wide variety of HID ballasts to operate the wide variety of metal halide, high pressure sodium and low pressure sodium available in todays marketplace. Like fluorescent lamps, HID are gas discharge lamps. Light is produced by and arc discharge between two electrodes located at opposite ends of an arc tube within the lamps outer glass envelope. The ballast is the lamps power supply, providing the proper starting and operating current and voltage to start and sustain this arc.