The Remote Focus Unit, commonly called an RFU (Pronounced arr-foo. For pronunciation help please see http://www.talklikeapirate.com/) for older consoles is a "riggers remote" control that allows basic remote control of the desk, to allow for turning channels on and off during the focusing process, patching and simple cue work.
Two examples of the Remote Focus Unit for the original Expression family (commonly referred to as Expression 1) are shown below.
It may be easy to confuse the black colored Expression 2 and Expression 1 Remote Focus Units. The easiest way to tell them apart is that the Expression 1 Remote Focus Unit has red LED displays.
With the older consoles desks, the RFU was either wired or wireless (see RRFU for details on the wireless version).
The most common problem with the RFU is an issue in the wiring. As the unit is moved extremely frequently during operation it is very common for the cable to wear out, particularly at the cable entry gland point.
The best solution to this is to re-terminate the end of the cable inside the RFU unit. A pinout for the connections to the older consoles RFU can be found in the manual.