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<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>There are a lot of factors that
impact this. First, CAT 5, while usable is overkill. Cat 3
(otherwise known as I/O wire) works equally well for voice grade lines.
That being said, for that long a run, a heavier gauge wire would be
better. I believe telcos use 18 – 22 guage (Cat 5 and Cat 3 are
both 26 awg). This has less resistive loss. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Most FXS or ATA devices use 24
volts or less for “battery”. That works fine for short loops,
but limits the range. A central office POTS port normally uses 48 VDC which
works well to several KM. If the customer is at the end of a long run in
a rural area, they use a “long line” card which uses 75
volts. (In rural communities, they often place the line cards in a
roadside “remote terminal” and use statistically multiplexed T1s to
make it appear to the switch as a part of it.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>That addresses the DC
characteristics, which can be reduced to ohms law. A phone needs around 8
V @ .02 A. The wire resistance determine the drop (E = IR) and the source
voltage determines whether there will be enough left. The A.C.
characteristics are more complicated. The FXS must do a 2 wire to 4 wire
conversion, which involves matching the impedance of the line. The FXS is
generally designed for relatively short lines, so might not be able to match either
the resistance or capacitance found in a long run. Heavier wire will
minimize this. In addition to that, the transmit side of the 2 wire to 4
wire circuit must be able to drive the load it sees, and again it may not be
designed with a long run in mind. Finally, COs line cards have the
ability to adjust receive and transmit gain to compensate for sound level
losses in long lines. While this isn’t routinely done on simple
circuits, it is an option an FXS doesn’t generally have. In
addition, the more gain that is inserted, the harder it is to balance to 2 wire
to 4 wire circuit, and the more complex it has to be in order to support this.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Wilton<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
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