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Path: utzoo!linus!decvax!mcnc!unccvax!dsi
From: dsi@unccvax.UUCP (Dataspan Inc)
Newsgroups: net.dcom
Subject: Re: 2-line phone and modem problems
Message-ID: <265@unccvax.UUCP>
Date: Sat, 10-Aug-85 10:54:39 EDT
Article-I.D.: unccvax.265
Posted: Sat Aug 10 10:54:39 1985
Date-Received: Wed, 14-Aug-85 00:30:07 EDT
References: <427@ucdavis.UUCP>, <1378@cbosgd.UUCP>
Organization: UNC-Charlotte
Lines: 34


       This might be a case of the AML/SSL(?) device giving a lot of problems.
These units look like a very large lid for ladies' powder, coloured the 
obligatory telephone grey, and are screwed to the wall near the telephone
in question.  What this little turkey does (evidently) is multiplex a second
telephone circuit on the present subscriber loop.  There is also a trap
which notches out the various carriers, etc. to control the AML unit - 
for the regular lines on the ** other ** loop.

      AML units are not noted for their tremendous linearity and distortion
characteristics.  In addition, they have a on-board battery (charged by the
-48 v from the CO) which runs down after about an hour of talking.  If
some turkey keeps ringing your phone while you are away, you get a dead 
battery in about 5 minutes. ( Even if your modem did work through it, the
AML signal quality deteriorates rapidly because of this....)

      You can't (fer sure) use a UDS 9600 A/B over one of the Continental
Telephone AML's; but the outside trap for the host line doesn't seem to
affect this modem.  However, most yuppie modems don't have automatic adaptive
equalisation, and might get screwed up by the group delay characteristics
of this filter (it didn't have to be linear phase for the original purpose).

       Try the other telephone line, and look for an AML unit near one
of your telephones; or a trap (it is usually stamped with the Continental
Telephone logo) near the loop arc suppressor outside.  If you have to get
rid of an AML and insist on a real dry pair, DO NOT TELL THEM IT IS FOR DATA
but rather that you are a doctor (or something) and need more reliable
communications...the battery running down is a real inconvenience.

See, your phones must have some frequency response past 3 kHz.....


David Anthony
DataSpan,  Inc