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<BODY bgColor=#ffffff>>You should not get that message on analog lines in the
USA or Canada. I <BR>>suspect your line has a provisioning issue or is
using different <BR>>signaling than you think it is using.<BR><BR>
<DIV><FONT face=Arial size=2>Not necessarily true. Most recent solid state
switches have abandoned this as a cost saving measure.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Polarity reversal was originally done on all loop
start and ground start circuits on the calling end when the called party
answered. It was used to identify start of call. On a relay based
step switch it was fairly easy to do, because the path went through a relay
contact that changed at that point anyway, so it was just deliberately wired
backwards.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>It created havoc with early DTMF pads, because they
used transistors and needed a known polarity. That was solved by adding a
bridge rectifier in the dialpad.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Loop and Ground Start trunks can still be ordered
with this option because it helps accurately determine start of call for
CDR. However, it requires a more expensive line card in the CO, so they
don't like to do it. A similar switch when a call is first terminated
(sometimes before it rings) can be used to insure that a line is not
accidentally picked for an outgoing call by a PBX when a call is coming in on
it.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Wilton</FONT></DIV>
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