Date: Sun, 15 Sep 91 18:58 PDT
From: John Higdon <john@zygot.ati.com>
Organization: Green Hills and Cows
Subject: Re: Monkey Business (or Pair-Hunting in Toronto)

Jamie Mason <jmason2@utcs.utoronto.ca> writes:

> What do you people know about these AML-II boxes?

I am shocked. It is incredible that a class act like Bell Canada would
stoop to such nonsense. What you describe (in fact the whole story) is
GTE through and through. Subscriber carrier is the worst disaster that
could befall you and your house. The unit you describe encodes and
decodes a subcarrier on a pair. The 'metallic' customer is the
non-muliplexed phone and the 'carrier' customer (you) uses the
subcarrier.

My first suggestion (short of demanding the thing be ripped out by the
roots) is to supply that "6-8 volts" you mentioned from a suitable
transformer. Any old "princess" or "trimline" transformer will do.
Why?  because if you use the phone a lot and get a lot of calls, the
NiCad will eventually die since it can only charge when you and the
metallic customer are off the phone. You will know the battery is
dying when there is so much noise and distortion that you can no
longer converse over the line.

The reason you detect a difference in your ringer sound is that
instead of a nice, hefty twenty hertz ring current coming from the CO,
you are getting a locally produced (in that box) ring current that is
a ghost of what comes from real CO equipment. Also, the ring will
sound different depending on the charge in your battery at the moment.

I was the carrier subscriber once. What I did not know was that at one
point GTE terminated the service of the metallic customer, battery and
all. Slowly, but surely, the quality of my telephone conversations was
going down the tubes. Finally, suspicious that the battery was
croaking, I checked the pair and found no dial tone or battery on the
metallic side. Connecting a transformer to the unit perked up my
telephone once again, but I finally got GTE to convert my service to
metallic.

> Since this is a
> multiplexer, it (by definition) reduces the bandwidth of each of the
> lines it is on.  I am told a copper pair has *much* higher bandwidth
> than a single phone line, so there should be no problems with my modem
> (2400 baud).  Has anyone had experience with this type of installation?  

I never tried using a modem over the blasted thing. In theory there
should be no problem. But who knows how good the phase integrity is or
how linear the response is? If no one else responds, you can report
back to us.

> Am I going to get line noise? How good is the isolation: am I going to
> experience crosstalk?  Are there any juicy tidbits of information
> about these boxes or personal experiences with them which you would be
> willing to share?  :-)

It will be more noisy than a straight phone line, but not much. You
will lose CPC (loop signal) from the CO. There is no crosstalk. The
"isolator" that you found simply protects you (the carrier customer)
from anything that the metallic customer might do such as short the
line, etc.

These boxes are known in the biz as "GTE's substitute for adequate
facilities". Again, it is almost impossible to believe that any
company with 'Bell' in the name would stoop so low. You are right:
this is way beneath Pac*Bell, who has never failed, albeit after much
moaning, to provide requested facilities in a timely manner. And PB
has NEVER used those rotton subscriber carrier devices!


        John Higdon         |   P. O. Box 7648   |   +1 408 723 1395
    john@zygot.ati.com      | San Jose, CA 95150 |       M o o !