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From: rkane@BBNCC5.ARPA (Richard Kane)
Newsgroups: mod.telecom
Subject: what is an AML and how does it work?
Message-ID: <8510242050.AA16641@UCB-VAX>
Date: Thu, 24-Oct-85 15:25:00 EDT
Article-I.D.: UCB-VAX.8510242050.AA16641
Posted: Thu Oct 24 15:25:00 1985
Date-Received: Fri, 25-Oct-85 03:32:30 EDT
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I moved into a new apartment last month and had quite a bad experience
getting phone service.  Several weeks before I actually moved, I ordered my
new phone service with New England Telephone and was told that there would
be no problem in setting up my new service on time.  Since I was only
moving across the street from where I had been living, I wanted to keep my
existing phone number, but I also wanted to have a second line installed
with a new number for my home terminal (I didn't tell NET that that was
what it was for).  

To make a very long story a bit shorter, when the installer came down on
the day that I moved, he discovered that they couldn't give me any phone
service at all since there were no more "facilities" (spare trunks)
available in my neighborhood.  (My apartment was wired up, but there were
no spare lines in the basement coming in from the street). After 2 weeks of
calling (from work) and badgering them almost every day, NET decided to
provide service to me by way of an AML.  An AML is apparently some sort of
multiplexor which is able to provide service for 2 (or more) phone numbers
over a single pair of wires.  The AML takes one number as input and gives
another number as output.  (There is apparently another AML or similar
device at the central office end of the circuit).  The configuration is
depicted below.


line in (main number)             |---|
__________________________________|AML|______________ second
		    |             |---|               phone
		    |                                 number
		 |------|
		 |filter|
		 |------|
		    |
		    |
		    |
                 main phone
                   number


Since I wanted two lines (numbers) coming into my apartment, and since it
was not convenient to run another set of wires up to my apartment from the
basement, the phone company came down and installed two AMLs in the
building.  

One AML was installed in the basement.  This AML was used to provide
service to two residents of my building who had previously had dedicated
lines of their own.  These residents were not informed of this change, but
it all should have been transparent to them anyway.  This thus freed up a
dedicated pair of wires to connect to the wire going up to my apartment.

The second AML was installed in my apartment.  This AML now provides me
with the two lines which I had originally requested and everything works
fine.

One more interesting thing to report about this whole affair is its effect
on my telephone answering machine.  For some reason unknown to both me and
the phone company, my answering machine will not answer calls when it is
hooked up to the line which is output from the AML, but works fine on the
primary incoming line.  Anyone have any ideas?