The D-2 is a dual mode, universal detector system which can be retro-fitted to your older GC. The D-2-I is optimized for trace level work in the helium photoionization mode.The stand-alone systems include detector, controller, electrometer, helium purifier, and power supply.Available for 110 VAC and 220 VAC.Pulsed Discharge Detector Model D-4 is single mode, optimized for trace level work in the helium photoionization mode. Versions are available for easy installation on the Varian 3800; Shimadzu 14, 17, 2010, and 2014; ThermoFinnigan Trace, Mega, and Top; and Hewlett Packard 5890.With the exceptions of the universal version and the HP 5890 version, the detectors use the FID electrometer of the existing GC.