On Sep 24 21:38 96, Paul Wankadia of 3:640/772.3 wrote:

PW> On 09 Sep 96, Danny Keogh wrote to Jason Smith --

DK>> Have you ever tried reading the manuals for some modems.  You
DK>> have to be a bloody communications expert to understand half the
DK>> stuff in them.

PW> Yes -- could someone (anyone?) explain what that polynomial supposedly 
PW> called "scrambling" is for?

The scrambler function is to control the statistical probability function
of the encoded signal.  Without a scrambler, the probability of steady 1
and steady 0 are pretty high.  With an adequate pesudo-random overlay,
NOTHING gets a favoured look-in.  

Bingo - the maths pay off, and the spectrum is used evenly.  Without, the
signals lump up, and the bandwidth isn't used evenly - Nyquist sez that's a
no-no - and is right.  Uneven use means tradeoff of signal/noise ratio, not
getting the throughput you should.

A "perfect" modem transmission would be sending pure white noise
as the encoded signal.  The scrambler pretends this is so, to a moderate
degree of success.

  And what do half of those TLAs actually MEAN 
(I know
PW> what some of them STAND for, but what do they MEAN?) ...?

Lots of people are too lazy to string together jawbreaker words, AND they
like to look smart at the same time...:-)

Regards,
Dave Hatch.

--- Msgedsq 3.20