| Title: | FDDI - The Next Generation |
| Moderator: | NETCAD::STEFANI |
| Created: | Thu Apr 27 1989 |
| Last Modified: | Thu Jun 05 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2259 |
| Total number of notes: | 8590 |
Striking out too early ?! Scenario: Customer has bought DECconcentrator 500 with Thinwire and STP modules and DECstations 5000s with copper DEFZAs. Has been using in ad-hoc manner via "local" cabling. Recently customer has had structured wiring system installed (not by us) but has heard and taken advice about Category 5 cabling so as to support TP-DDI (or whatever it's called this week !) Problem: Now wish to relocate the FDDI users to their desks and - using the existing FDDI kit - connect them using the new super-duper wiring scheme. Oops - it doesn't seem to work ! Apparently they've tried using very short samples (2 metres) of the UTP cable with the STP DEFZA and DEFCN kit with no luck. I suppose this is to be expected and may "teach them a lesson" etc., but is there anything we can do/suggest that may be of assistance in the immediate timeframe while we await the arrival of the new UTP modules ? More to the point, will the likes of Synoptics and the rest of the gang of 5 be able to offer UTP equipment that will (or claim to) satisfy the customer need now and as/when the UTP standard is ratified ? I don't want to see us lose the customer if possible. Thanks Rog
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 1032.1 | KONING::KONING | Paul Koning, A-13683 | Tue Jul 20 1993 17:56 | 11 | |
About the only things STP and UTP have in common is that they are both copper cable and both have twist in them. Apart from that, they are totally different. There's no way that an STP-specific design can possibly be made to work on UTP. The only two alternatives I can think of are: 1. Reinstall the STP cable (leaving the UTP would make sense). 2. Wait for UTP modules. Talk to product managers about earliest possible arrival of UTP modules. paul | |||||
| 1032.2 | could a balun help | PERE::BRUCE | Wed Jul 21 1993 10:53 | 2 | |
You may be able to find a Balun in the black box catalog for a totally
unsupported short term fix
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| 1032.3 | KONING::KONING | Paul Koning, A-13683 | Wed Jul 21 1993 13:40 | 9 | |
No. Baluns convert from coax to twisted pair. That's what the name means: "BALanced to UNbalanced". If I remember right, there is indeed an impedance difference between STP and UTP, which a transformer could compensate for. But that's only a very small part of the difference. The bigger problem is that the signal is much cleaner on STP, so an STP-only design has very little chance of operating on UTP. (Conversely, a UTP design should be able to handle shielded cable, provided the impedance issue is addressed.) paul | |||||
| 1032.4 | Can't forget about cable detect | LEVERS::MELARAGNI | Wed Jul 21 1993 13:47 | 6 | |
You can't just add a balun to STP and expect it to work. There is a cable detect circuit in the STP adapters that must see a DC voltage before it will wake up and create a link. Ordinary baluns do not pass the DC voltage required for this cable detect circuit. bill | |||||