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Conference netcad::hub_mgnt

Title:DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:NETCAD::COLELLADT
Created:Wed Nov 13 1991
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:4455
Total number of notes:16761

3795.0. "connecting async devices to repeater port? what happens?" by WOTVAX::ppp3.olo.dec.com::davet (plug and pray ...) Mon Aug 19 1996 11:11

What happens if an async device such as modem/terminal/fax machine is 
'accidentally' connected to a 900TP repeater port?


Does the device detect the error and auto-partition / disable the port?
Is management software notified by way of a trap?

Do all our current repeaters behave in the same fashion?


many thanks
dave




T.RTitleUserPersonal
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3795.1Your guess is as good as mineNETCAD::GILLISTue Aug 27 1996 18:5150
For repeater ports to autopartition, they need to see something along the
order of 32 successive collisions on their Rx pair.

Async devices have different pin assignments than repeater ports. You
may or may not do damage to the drivers on either device ...


8-pin modular jack pin-out for connecting to repeater ports
 (only pins 1,2,3,6 used for 10BaseT)
---------------------------------------------------

1 Tx+
2 Tx-
3 Rx+
6 Rx-

Furthermore, 10BT ports on our repeaters (and just about everyone's)
are wired in a "crossover" fashion, so that a "straight-thru" cable
can be used to connect a station to a repeater directly.
Therefore, this is the wiring on your repeater PORT:

1 Rx+
2 Rx-
3 Tx+
6 Tx-

I have no idea what wiring standard is used on your modem device ...
there are so many standards (RJ-11, RJ-12, RJ-45, for starters).
Chances are it uses RJ-45, though.

Async Ports - RJ-45 Standard for async devices
-----------------------------------------------
1 RNG
2 DTR
3 XMT
4 XMTGND
5 RCVGND
6 RCV
7 DSR/DCD
8 unused

If you used a "straight-thru" cable when accidentally connecting
a modem to a repeater port, it sounds like pin 3 could give you trouble,
as both devices are transmitting on the same pin.

Like I said, you're guess is as good as mine, but avoid it at
all costs!

John Gillis
clearVISN developer