"Larry Jaques" wrote in message
...
On Mon, 14 Nov 2016 01:15:49 -0500, "Michael A. Terrell"
wrote:

DoN. Nichols wrote:

Well ... 25-pair cables *are* 50 wires, and the dots on solid
uniquely marked each wire in that count. (Aside from that, the two
wires
in a pair were also twisted -- to minimize crosstalk to adjacent
pairs.)
The twisting helps keep them together so you don't have to search
through 49 other wires to find the other half of a pair. :-)


Not only re he pairs twisted, but the twist rate varies from
pair to
pair to reduce the crosstalk even further.

They probably researched the hell out of that to end up with what
they
did. I'm sure digital/optical tech is even more heavily researched
as
the 2.5Gbs trunks get over 40k conversations or 250 TV channels
simultaneously. (I'm sure it's much faster now.) Zimply Amazing.


The mathematics of communications theory is the most difficult subject
I've tried to learn, worse than Thermodynamics or Nuclear Physics. A
good introduction is the encoding on a music CD:
https://www.usna.edu/Users/math/wdj/...s/reed-sol.htm

Transmission line math is bad enough:
http://www.antenna-theory.com/tutori...ine.php#txline

Thankfully Mitre paid for and provided rooms with TVs, VCRs and phone
links to local university night school courses in electrical
engineering so I could learn how to do my very challenging job.

--jsw