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<dt><font size="4"><b><big>The VoIP Payphone Idea <br>
</big></b></font></dt>
<dt><big> <br>
</big></dt>
<dt><big>By William Flanagan</big></dt>
</dl>
<big>Remember the public phone booth by the side of the road? </big><big>Plain
Old Telephone Service (</big><big>analog technology</big><big> POTS
lines) </big><big>worked pretty well without environmental controls.</big><big>
</big><big>Cell phones have almost eliminated phone booths, but </big><big>we
still have work environments in tough neighborhoods like
power substations, pit heads at mines, and remote railway switch
points. Multi-tenant building with no air conditioning in the wiring
closets qualify as harsh, too. <br>
<br>
Moving from circuit switching to IP introduces three key concerns. <br>
</big>
<ol>
<li><big>Power for active routers/switches where passive copper loops
needed none. </big></li>
<li><big>Cooling for that electronic equipment. </big></li>
<li><big>Extending Ethernet LANs to match the reach of analog phone
lines.</big></li>
</ol>
<big>Sales literature for VoIP equipment typically shows high-end
phones on executive desks or in business call centers. The assumption
is that the user and the wiring closet enjoy a controlled "office"
environment. It ain't necessarily so when the phone system extends
beyond the office.<br>
<br>
</big><big></big><big></big><big>Electrical power is seldom a problem.
The utilities will drop a feed if you're willing to pay. For low-power</big><big>
equipment</big><big> you can deploy a solar panel and a storage battery
to run through the night, or a fuel cell. Low drain reduces the cost
of power infrastructure. <br>
<br>
There are items that boast of low power. Snom says its model <a
href="http://www.snom.com/en/products/ip-phones/snom-300-ip-phone/">300
IP handset</a> is the lowest, at 1.7 to 2.7 watts. Encore Networks has
a ruggedized <a href="http://encorenetworks.com/click_ds_BANDIT_2.htm">router</a>
that draws only 7 W. That's a total of less than 1 amp at 12 V for
voice and data connectivity. These days, wherever voice is wanted
there's almost always a need for data as well, so it's best to budget
for both.<br>
<br>
With power that low, the need for cooling may disappear. Encore's
router is hardened to operate in ambient temperatures from -40 to 85 C
(-40 to 193 F)--and that's not a typo, that's the<a
href="http://ieeexplore.ieee.org/Xplore/login.jsp?reload=true&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F8014%2F28253%2F01263435.pdf%3Farnumber%3D1263435&authDecision=-203">
IEEE 1613 standard</a>. Phones to cover that range are "less common": </big><big>
most phone are </big><big>4 to 40 C (40 to 104 F)</big><big>. </big><big>
Cisco's <a
href="http://www.cisco.com/en/US/prod/collateral/voicesw/ps6788/phones/ps10326/data_sheet_c78-584412.html">6901
IP phone</a>, relatively low power at 3.11 W, is rated for -5 to 45 C
(23 to 113 F). </big><big> An interesting exception is a <a
href="http://www.ctiusa.com/electronic_systems/enviroxtreme.html">ruggedized</a>
adaptation of the Cisco 7961 IP phone that's "dust proof," but it
needs a heater for the LCD when it's cold.<br>
</big><big><br>
In a migration from a legacy switch to VoIP, we can assume a copper
loop is in place, perhaps even a 4-wire cable capable of T-1
transmission. Old copper is not much good for native Ethernet, as in
10 Mbit/s LAN, but </big><big>well-proven technologies (ISDN BRI or
PRI, DSU/CSU, or DSL) can p</big><big>ush IP and Ethernet over legacy
cable for more than a mile. These digital services from a local
exchange carrier (LEC) typically cost more than the existing POTS line,
but enterprise versions of the hardware are available if you have the
right of way or own the cable. As an alternative, Encore's router
offers an internal cellular radio (for a data service) in addition to a
CSU (one can back up the other for higher availability). <br>
<br>
VoIP payphones don't look like a hot item with LECs</big><big> in the
US.</big><big> More likely the technology will find use in private
networks, for control functions (think SCADA protocol) and voice
connections on sprawling infrastructure such as power lines, pipe
lines, and railroads. To</big><big> find IP versions of real payphones
look on the WWWeb--not at the side of your road.</big><br>
<br>
__<br>
<dl>
<dt> <b>How Can Flanagan Consulting Help You?</b> <br>
We understand not only the technology of networks, but also<br>
the surrounding business processes: procurement, bid<br>
preparation/analysis, statements of work, financial analysis,<br>
consensus building around a solution, and more.</dt>
<dt><b> Find out now: call +1.703.242.8381</b> or email <b><a
href="mailto:Bill@Flanagan-Consulting.com">Bill@Flanagan-Consulting.com</a></b></dt>
<dt>___<br>
</dt>
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We have assisted attorneys preparing claims, depositions, and
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How can we help you? Queries to +1.703.242.8381.</dt>
<dt>___<br>
</dt>
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<dt><b>__</b></dt>
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