26 Aug
2016
26 Aug
'16
7:56 a.m.
On Aug 26, 2016, at 10:24 AM, Joseph Zatarski
<jzatar2 at illinois.edu> wrote:
...
Yes, the whole reflection thing could get into a bit of a complex
discussion involving transmission line theory, but I am an electrical
engineer, so here goes:
Yes, you need proper termination at either end, or else you get the wrong
voltages on the line and cause 'collisions' (well, detect collisions
anyway, though there aren't really any until the first reflection comes
back from the cable end).
That reminds me of an amusing error in a 1980s trade rag for DEC users ("The DEC
Professional"). It discussed how you could mix 10Base5 and 10Base2 hosts by coupling
the two size coax cables through an N to BNC adapter. That's fine so long as you use
the 10Base2 limits. But instead of a barrel adapter, the article had a photo showing a T
connector at the transition, with a "terminator" attached to it. So that
network had three terminators: one at each end and one in the middle. I suspect it
didn't work, or at least quite poorly.
paul