Sky digital support forum at Sats UK, Everything involved on the hardware and software side of reception of the channels from 28.2/28.5 East BskyB, special focus on fringe reception of Astra 2D for UK free to air channels
My System: Sky HD, TM6800HD, Manhattan Plaza ST550 and TM1500 CI+. 1.0m dish and 36v motor, Panasonic DVD HDD recorder and Panasonic video/DVD recorder. Sony G800 HD TV stand/surround system + Sony KDL40W2000. Infinity USB, Elvis, CAS1, CAS2.
As far as I know the port does not have a function at present. It's probably there as part of the 'future proofing' for possible future software downloads.