A Remote Focus Unit (RFU) is a remote control for a lighting desk. Most newer ETC desks use radio, network, or USB remotes, however older desks like Express, Expression and Obsession used cabled RFUs.
The cable used was three pair cable, and the connector was a six pin XLR. Note that there are two variants of six pin XLR, one of which - "Switchcraft Type" - is symmetrical, the other of which - "Neutrik Type" is not symmetrical. It is important to ensure you use the correct type if repairing an RFU or making an extension cable.
RFUs use the "Switchcraft Type" XLR.
When installing RFU, ETC recommends using Belden 9728 cable or an equivalent. Because of the high current requirements of the RFU, two separate cables are pulled for the 0v and +12v lines; these cables should be of size 16AWG (or 1.5mm2).
The maximum length RFU data may be run is 500' (150m).
If using Belden 9728 the cable color code should be to use the red/black pair for pins 1/2, the white/black pair for pins 3/4 and the separate red/black pair of singles for pins 5/6.