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<title>Chapter 25 -- TAPI Hardware Considerations</title>
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<h1><font COLOR="#FF0000">Chapter 25</font></h1>
<h1><b><font SIZE="5" COLOR="#FF0000">TAPI Hardware Considerations</font></b> </h1>
<hr WIDTH="100%">
<h3 ALIGN="CENTER"><font SIZE="+2" COLOR="#000000">CONTENTS<a NAME="CONTENTS"></a> </font></h3>
<ul>
<li><a HREF="#ModemsandtheUniModemDriversforWin9">Modems and the UniModem Drivers for Win95
and WinNT</a> <ul>
<li><a HREF="#AQuickReviewofHowModemsWork">A Quick Review of How Modems Work</a> </li>
<li><a HREF="#TheUniversalModemDriversandTAPISer">The Universal Modem Drivers and TAPI
Service Providers</a> </li>
</ul>
</li>
<li><a HREF="#BasicDataModems">Basic Data Modems</a> </li>
<li><a HREF="#DataModemswithVoice">Data Modems with Voice</a> </li>
<li><a HREF="#TelephonyCards">Telephony Cards</a> </li>
<li><a HREF="#Summary">Summary</a> </li>
</ul>
<hr>
<p><font COLOR="#000000">In this chapter, you'll learn the differences between the three
primary types of telephony hardware for pcs:</font>
<ul>
<li><font COLOR="#000000">Basic data modems</font> </li>
<li><font COLOR="#000000">Voice-data modems</font> </li>
<li><font COLOR="#000000">Telephony cards</font> </li>
</ul>
<p>These three types of interface cards provide a wide range of telephony service for
desktop workstations. You'll learn the advantages and limits of each of the interface card
types and how you can use them in your telephony applications. </p>
<p>Basic data modems can support Assisted Telephony services (outbound dialing) and
usually are able to support only limited inbound call handling. </p>
<p>Voice-data modems are a new breed of low-cost modems that provide additional features
that come close to that of the higher-priced telephony cards. These modems usually are
capable of supporting the Basic Telephony services and many of the Supplemental services.
The key to success with voice-data modems is getting a good service provider interface for
your card. </p>
<p>Finally, telephony cards offer the greatest level of service compatibility. Telephony
cards usually support all of the Basic Telephony and all of the Supplemental Telephony
services, including phone device control. Most telephony cards also offer multiple lines
on a single card. This makes them ideal for supporting commercial-grade telephony
applications. </p>
<p>You'll also get a quick review of how modems work and how Win95 and WinNT use modem
drivers to communicate with hardware devices. </p>
<h2><a NAME="ModemsandtheUniModemDriversforWin9"><font SIZE="5" COLOR="#FF0000">Modems and
the UniModem Drivers for Win95 and WinNT</font></a></h2>
<p>All TAPI services are routed through some type of modem. These modems also depend on
the Windows operating system to supply device drivers to communicate between programs and
the device itself. While a detailed discussion of device drivers is beyond the scope of
this book, it is a good idea to have a general understanding of how Windows uses device
drivers and how modems work. In this section you'll get a quick review of modem theory and
a short discussion of the Universal Modem Driver that ships with Win95 and WinNT. </p>
<h3><a NAME="AQuickReviewofHowModemsWork">A Quick Review of How Modems Work</a></h3>
<p>Before getting into the details of how the three types of telephony hardware differ, it
is important to do a quick review of how modems work. If you've seen all this before, you
can skip to the next section. </p>
<p>Sending computer data over voice-grade phone lines is a bit of a trick. All data stored
on a pc (documents, programs, graphics, sound and video files, and so on) is stored as 1s
and 0s-binary data. However, standard telephone lines are not capable of sending binary
data-only sounds. That means that any information sent over the telephone line has to be
in the form of sound waves. In order to accomplish this feat, hardware was invented to
convert digital information into sound (that is, to <i>modulate</i> it), then back again
from sound into digital information (<i>demodulate</i> it). This process of modulating and
demodulating is how the device got its name: mo-dem (<i>mo</i>dulate-<i>dem</i>odulate). </p>
<p>Sending data over phones lines involves three main steps. First, a connection must be
established between two modem devices over a telephone line. This is typically done by
having one modem place a telephone call to the other modem. If the second modem answers
the telephone call, the two modems go through a process of determining if they understand
each other called <i>handshaking</i>. If that is successful, then information can be
passed. </p>
<p>In the second step, the digital information is modulated into sound and then sent over
the voice-grade telephone line to the second modem. In the last step, the modem at the
other end of the call converts (demodulates) the sound back into digital information and
presents it to the computer for processing (view the graphic, save the file, play the
video or audio, and <br>
so on). </p>
<h3><a NAME="TheUniversalModemDriversandTAPISer">The Universal Modem Drivers and TAPI
Service Providers</a></h3>
<p>TAPI requires each workstation to have not just a TAPI-compliant application, but also
a <i>Telephony Service Provider Interface</i> (<i>TSPI</i>). This interface talks directly
to the hardware to convert your TAPI service requests into commands understood by the
hardware. The TSPI is usually supplied by the hardware vendor, but Microsoft Win95 ships
with a simple TSPI called the <i>UniModem Driver</i> (Universal Modem Driver). The
UniModem driver is designed to support Assisted Telephony and some Basic Telephony. You
can build simple applications that allow users to place and receive voice and data calls
using basic data modems and the UniModem driver that ships with Win95 and WinNT. </p>
<div align="center"><center>
<table BORDERCOLOR="#000000" BORDER="1" WIDTH="80%">
<tr>
<td><b>Note</b></td>
</tr>
<tr>
<td><blockquote>
<p>You'll learn more about TSPI and modem drivers in <a HREF="ch27.htm">Chapter 27</a>,
"TAPI Behind the Scenes-The <tt><font FACE="Courier">TELEPHON.INI</font></tt>
File." </p>
</blockquote>
</td>
</tr>
</table>
</center></div>
<p>Microsoft has released a modem driver that supports additional voice features including
playing and recording audio files. This driver is called the <i>UniModemV Driver</i>
(Universal Modem for Voice). This driver supports the use of voice commands along with
recording and playing back voice files. It can also handle caller ID and some other added
service features. Exactly what the UniModemV driver can do is also dependent on the
hardware. The telephony hardware must recognize any advanced features and be able to
communicate them to the driver. </p>
<div align="center"><center>
<table BORDERCOLOR="#000000" BORDER="1" WIDTH="80%">
<tr>
<td><b>Tip</b></td>
</tr>
<tr>
<td><blockquote>
<p>You can find a copy of the UniModemV driver on the CD-ROM that ships with this book.</p>
</blockquote>
</td>
</tr>
</table>
</center></div>
<h2><a NAME="BasicDataModems"><font SIZE="5" COLOR="#FF0000">Basic Data Modems</font></a></h2>
<p>The most basic type of hardware that supports TAPI is the basic data modem. This type
of modem is designed to use analog phone lines to send digital data. Any computer that can
access online services (BBS, Internet, commercial information services, and so on) has at
least this level of modem hardware. You can get basic data modems with speeds of 9600 to
14,400bps (bits per second) for $100 U.S. or less. You can get data modems that can handle
28,800bps for a bit more. </p>
<p>It is not easy to find data modems for pcs that are rated beyond 28.8Kbps. The primary
reason for this is that voice-grade telephone lines cannot handle error-free throughput at
speeds much faster than 28.8Kbps. Although there are now some 33.3 modems on the market,
your local lines may not be able to handle those speeds. You can contact your local
telephone service provider to get an idea of the line quality in your area. Usually, if
you want to use speeds faster than 28.8, you'll need to purchase special lines from your
local telephone service provider. </p>
<p>Almost all basic data modems recognize a common set of control codes. This set of
control codes is called the <i>Hayes</i> or <i>AT</i> command set. This set of controls
was developed by the makers of the Hayes modem. The first command in the set (<tt><font
FACE="Courier">AT</font></tt>) is the "attention" command. This tells the device
you are about to send control codes directly to the hardware. The command set is known by
the original author's name ("Hayes") or by the first command in the set
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