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<td bgcolor="#336666"><b><font face="Arial" size="2" color="#FFFFFF">2.2</font></b></td>
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<strong><font face="Arial" size="2" color="#FFFFFF">WAN Technologies</font></strong></td>
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<td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
2.2.1</font></b></td>
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<font face="Arial" size="2" color="#FFFFFF">Analog dialup</font></strong></td>
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<font FACE="Arial" SIZE="2">
When intermittent, low-volume data transfers are needed, modems and
analog dialed telephone lines provide low capacity and dedicated
switched connections.
<img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"></font><p>
<font FACE="Arial" SIZE="2">
Traditional telephony uses a copper cable, called the local loop, to
connect the telephone handset in the subscriber premises to the public
switched telephone network (PSTN). The signal on the local loop during
a call is a continuously varying electronic signal that is a
translation of the subscriber voice.</font></p>
<p>
<font FACE="Arial" SIZE="2">
The local loop is not suitable for direct transport of binary computer
data, but a modem can send computer data through the voice telephone
network. The modem modulates the binary data into an analog signal at
the source and demodulates the analog signal at the destination to
binary data.</font></p>
<p>
<font face="Arial" size="2">The physical characteristics of the local
loop and its connection to the PSTN limit the rate of the signal. The upper limit is
around 33 kbps. The rate can be increased to around 56 kbps if the
signal is coming directly through a digital connection.</font></p>
<p>
<font FACE="Arial" SIZE="2">
For small businesses, this can be adequate for the exchange of sales
figures, prices, routine reports, and email. Using automatic dialup at
night or on weekends for large file transfers and data backup can take
advantage of lower off-peak tariffs (line charges). Tariffs are based
on the distance between the endpoints, time of day, and the duration
of the call.</font></p>
<p>
<font FACE="Arial" SIZE="2">
The advantages of modem and analog lines are simplicity, availability,
and low implementation cost. The disadvantages are the low data rates
and a relatively long connection time. The dedicated circuit provided
by dialup will have little delay or jitter for point-to-point
traffic, but voice or video traffic will not operate adequately at
relatively low bit rates.</font></p>
<p>
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</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<p>Checkbox: WAN Technologies Analog Dialup</p>
<p>Upon completing this activity, the student
will be able to identify the characteristics associated with an
analog dialup circuit.</p>
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<b>Web Links</b></font></p>
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<p>Dialup Technologies<p>
<a target="_blank" href="http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/dialup.htm">
http://www.cisco.com/univercd/cc/
td/doc/cisintwk/ito_doc/ dialup.htm</a></font></p>
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