5 Sep
2002
5 Sep
'02
11:29 a.m.
--- "Fred Cisin (XenoSoft)" <cisin(a)xenosoft.com> wrote:
Real world counter example:
VAX 11/750 in machine room with multiple Emulex CS/21 16-port serial
cards. Terminals in various offices strewn about a 3000 sq ft single-
story office/warehouse space. Telco 25-pair cables going from patch
panel in machine room, up to 18' high ceilings, along, then dropped
down into individual offices to provide 8 ports per office (Nevada
Western RJ-11 wiring system). Typical run - 150 feet from VT100 to VAX
over unshielded cable. Terminal speed - 9600 bps.
To wake the VMS terminal driver, one hit RETURN a couple of times. This
reliably produced one "u" echoed on the terminal per RETURN sent. Once
in use, no further ghosted characters appeared. Other than that,
the terminals were reliable. We even used the same wiring for Kermit
between machines in the machine room and at our desks (for those few of
us who had a development system in addition to the ubiquitous terminals).
So... 150-200 feet is OK for 9600 baud, but not entirely error free.
> similar.
422 by the way is specified to go almost 1000 feet, while
> with 232 you are lucky to get over 10 feet. Regards - Mike
On Thu, 5 Sep 2002, Sellam Ismail wrote:
> That's not true. Serial cable can go for a good many feet before the
> signal breaks down (someone should pipe in with actual data ;) It'll handle way more than its spec calls for.
When researching the
content for "RS232 Solution", Joe Campbell ran it through a couple of
thousand feet of wire (on a spool). Well, I guess that by being on a
spool, the two ends were less than 10 feet apart. :-)
Baud rate is part of the equation for transmission length with EIA-232.
The charts I've seen have a max length that tapers off at speeds over
1200 bps ISTR. The distance at 19200 bps is substantially lower than
even 2400 bps (50%?)
-ethan
P.S. - the cool part is that I have some of this stuff in my walls at
home - I have two 25-pair cables between the computer room and the
basement - one for phone, one for terminal sessions. It was nice
when I had multiple phone lines (fax/modem, home voice, home-office
voice). I'm down to one live voice pair out of 25, but the multiple
terminal lines are nice.
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