| 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 |
Hello,
customer wants to interconnect an IBM RS/6000 with STP-FDDI interface
(IBM No. 2725 FDDI STP-SR) and a DECconcentrator 900 equipped with
UTP interface.
According to IBM their interface conforms to TP-PMD. This would mean
that they also use MLT-3 en-decoding ??? Now if they do, would there
only be an impedance issue (100 Ohm vs. 150 Ohm) and could this be solved
by using a balun ?
Thanks in advance and regards
Ulrich
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 1374.1 | you'll need a good balun for that | 4371::MELARAGNI | Tue Jun 14 1994 19:38 | 18 | |
TP-PMD comformance means MLT-3 encoding. It also means data scrambling
and unscrambling as well as base-line wander tolerance.
In theory a balun would work here, but the balun would have need to
have a high bandwidth (>150 MHz) and really good
differential-to-common mode balance (>40dB over the frequency
range). I am not aware of any such baluns that have the correct
connectors on them to allow direct connection to UTP and STP. Such
baluns exist but are for lab use and do not have the correct
connectors. Also, they are expensive (>$150) and since you'd need two
(one for RX, one for TX) the total additional cost per link will be
$300. Ouch.
The other option is for us to produce an STP TP-PMD card. Plans for
such a beast are muddled at best and the liklihood of us producing such
a thing over the next 6 months is slim.
bill
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