SRA@wsmr-simtel20.army.mil (Gene N. Cartier) (11/11/90)
We are considering migrating one of our branch offices from an old NBI word processing system to a state-of-the-art system based on DEC 5000's running Ultrix and using X-Windows Terminals. The current environment uses one twisted pair in a six conductor sheath to support the NBI connection an additional pair is used to provide phone service via CENTREX from the telco. I have planned to support the new system using 802.3 using 10BaseT connections. The penny pinchers want me to use the existing wiring. This means that the 802.3 and CENTREX conductors will be in the same sheath. I remember reading somewhere that this is not a good idea because CENTREX ringing will poke holes in the data because of voltage differences. Even though it is more expensive I have recommended that we recable. Am I being an alarmist? Does anyone have any experience in this area and better yet can anyone provide me with some hard copy references that I can use to defend my position or ease my concerns. I'll consolidate all responses and post them. Thanks, Gene Cartier SRA CORP SRA@WSMR-SIMTEL20.ARMY.MIL (703) 558-7507
cafl@lindy.stanford.edu (Carol Farlow Lerche) (11/27/90)
The problem with using an existing cable to carry both voice pairs and 10BaseT Ethernet is not so much inductive coupling getting ringing into the data but rather the possibility that a telephone installer will place a live phone line _onto_ your 10BaseT connection one day.