As an exercise to combat insomnia, I once read Recommended Standard #232
revision D (RS232D), the thrilling sequel to RS232C, and there is no
reference to a distance limit. I have no idea who started the popular
50 foot myth as the distance limitation is dictated by the capacitance
of the interconnection between devices, most of which will be found
in the cable. Cables with only a few picofarads/foot are readily
available. Sheilded cables typically exhibit higher capacitance. The
less capacitance the better to preserve the signal to the far end of
the data hose. With the right cable you can go longer and still be legal,
even much further and still work just fine.
 
 
Bob Jankalski -- Ideal Computer Services
 
On Tue, 12 Sep 1995, Robert Manocchia wrote:
 
>      We ran twisted pair much further than the "official" HP spec of 50
>      feet and had no problem with terminals. We did have an occasional
>      problem with printers, but nothing serious enough to worry about.
>
>
> ______________________________ Reply Separator _________________________________
> Subject: Terminal Communications
> Author:  "Dave Trottier (John Abbott College)" <[log in to unmask]> at
> HMS-Internet
> Date:    9/12/95 1:52 PM
>
>
> We're seeking advice from folks who may have migrated from
> classics to ix machines but have retained RS-232 connectivity
> between their terminals and DTC's.
>
> We are in the process of migrating from a series 70 to a 928. On
> the 70 we were able to run terminals, using twisted pairs, over
> extensive distances of 500-800 ft. This was at 9600 baud without
> any multiplexors or line drivers.
>
> My understanding from the response center is that voltage on the
> ports (DTC72 with RJ45 interfaces) is less than that on the classic.
> Regardless, we know we're exceeding the RS-232 50 foot "limitation".
>
> Does anyone know of a quick method of remedying this problem; i.e.,
> of amplifying our signals so we may continue to use twisted pairs at
> thes distances? We are considering line drivers or muxes but are
> looking for the easiest practical solution (i.e., we don't want to
> move our DTC's from the Computer Room and start installing fibre
> optic cables, etc.).
>
> If you have any suggestions, please contact me at your convenience.
>
> Dave Trottier, Operations Manager, John Abbott College
> [log in to unmask]  or  (514) 457-6610, Ext. 206
>