ch25.htm

MAPI__SAPI__TAPI

(&quot;AT&quot;). </p>

<p>Basic data modems support Assisted Telephony services without any problem (that is, 
placing outbound calls). Most basic modems are capable of supporting some of the Basic 
Telephony services, including accepting inbound calls. However, if you want to perform any 
of the more advanced TAPI services, such as playing or recording audio files, you'll need 
more advanced hardware. Also, if you want to access advanced features available for voice 
telephones such as caller ID, call hold, park, forward, and so on, you'll need more than a 
basic data modem. Figure 25.1 shows the TAPI service levels and telephony hardware 
classes. The highlighted areas give you an idea of how basic data modems do in supporting 
TAPI services. </p>

<p><a HREF="f25-1.gif"><b>Figure 25.1 : </b><i>Basic modem support for TAPI services </i></a></p>

<p>If you are designing applications that allow users to select names or phone numbers and 
then place outbound voice or data calls, basic modems will work just fine. In fact, unless 
you are planning to add voice recording, playback, or other advanced telephony features to 
your application, the basic modem will provide all your TAPI needs. </p>

<h2><a NAME="DataModemswithVoice"><font SIZE="5" COLOR="#FF0000">Data Modems with Voice</font></a></h2>

<p>There is a new type of modem available that offers all the services of a data modem, 
but also has added support for voice services. These modems are often called voice-data 
modems (or data-voice modems). This hardware has additional programming built into the 
chips that will support advanced telephone features such as caller ID, call hold, park, 
forward, and so on. Just as basic data modems use the AT command set, the voice-data 
modems use an extension of that set called the <i>AT+V</i> command set (<i>AT plus Voice</i>). 
</p>

<p>AT+V modems cost a bit more than basic data modems. You can find them in the U.S. 
packaged with sound cards and other multimedia hardware. Generally the cost is about $250 
U.S. If the modem is part of a bundled multimedia kit, you could end up paying twice that 
amount. </p>

<p>Voice-data modems also require a TAPI-compliant modem driver in order to work with TAPI 
services. This driver is usually supplied by the hardware vendor. Microsoft also supplies 
a modem driver that supports voice services-the UniModemV driver. If your modem does not 
ship with a TAPI-compliant driver, you might be able to install the UniModemV driver to 
enable your voice features. </p>
<div align="center"><center>

<table BORDERCOLOR="#000000" BORDER="1" WIDTH="80%">
  <tr>
    <td><b>Tip</b></td>
  </tr>
  <tr>
    <td><blockquote>
      <p>A copy of the UniModemV driver ships with the latest version of Windows 95 and the new 
      Windows NT 4.0. If you have an older version of Windows 95 or Windows NT, you can use the 
      copy of UniModemV on the CD-ROM that ships with this book. </p>
    </blockquote>
    </td>
  </tr>
</table>
</center></div>

<p>A word of caution is in order when purchasing a voice-data modem. There are several 
modems on the market that offer voice, voice-mail, telephone answering, and other 
TAPI-like services for pcs. The thing to keep in mind is that many of them are not 
TAPI-compliant. While you may get a modem that can do all the things you want, it may not 
do it using the TAPI calls and you many not be able to program it using TAPI services. </p>

<p>As of the writing of this book, there are a handful of voice-data modem vendors that 
have announced the release of TAPI-compliant hardware. Here is a list of some vendors 
currently offering TAPI-compliant voice-data modems: 

<ul>
  <li><font COLOR="#000000">Compaq Presario Systems</font> </li>
  <li><font COLOR="#000000">Creative Labs Phone Blaster</font> </li>
  <li><font COLOR="#000000">Logicode 14.4 pcMCIA</font> </li>
  <li><font COLOR="#000000">Diamond Telecommander 2500</font> </li>
  <li><font COLOR="#000000">Cirrus Logic</font> </li>
  <li><font COLOR="#000000">Aztech Systems</font> </li>
</ul>
<div align="center"><center>

<table BORDERCOLOR="#000000" BORDER="1" WIDTH="80%">
  <tr>
    <td><b>Tip</b></td>
  </tr>
  <tr>
    <td><blockquote>
      <p>This list is growing all the time. For the most recent updates on this list you can 
      check the CD-ROM that ships with this book. You can also check out the Communications 
      Developer's Guide web site for updates on MAPI, SAPI, and TAPI development. Point your 
      browser to <tt><font FACE="Courier">www.iac.net/~mamund/mstdg</font></tt>. </p>
    </blockquote>
    </td>
  </tr>
</table>
</center></div>

<p>Voice-data modems with supporting TAPI drivers offer a wide range of access to TAPI 
services. You can use voice-data modems to perform both outbound and inbound call 
handling, play and record voice files, and (if the feature is available on the telephone 
line) support caller ID and other advanced services for single-line phones. Figure 25.2 
shows how voice-data modems shape up in their support of TAPI services. </p>

<p><a HREF="f25-2.gif"><b>Figure 25.2 : </b><i>Voice-data modem support for TAPI services </i></a></p>

<h2><a NAME="TelephonyCards"><font SIZE="5" COLOR="#FF0000">Telephony Cards</font></a></h2>

<p>The most advanced level of hardware you can get for TAPI services on a desktop pc is a 
dedicated telephony card. This is a piece of hardware dedicated to handling telephone 
services. Most telephony cards are designed to handle more than one line at a time, too. 
If you are planning an application that must answer several phone lines or perform any 
line transfers, and so on, you'll need a telephony card. </p>

<p>Most telephony cards are sold as part of a kit. You can get software development tools, 
cards for the pc, cables, and documentation all for one price. This price usually starts 
at around $1000 U.S. and can easily climb depending on the number of lines you wish to 
support. Even though the price is a bit high, if you are doing any serious TAPI work, 
you'll need this kind of equipment. </p>

<p>As with other telephony hardware, telephony cards need an accompanying TAPI driver in 
order to recognize TAPI calls from your program. While most telephony card vendors are 
working on TAPI drivers, not all of them supply one as of this writing. It is important to 
check the specifications of the hardware and supporting materials before you buy. </p>

<p>It is also important to point out that there are lots of very sophisticated hardware 
and software tools for handling telephony services that are not TAPI-based. It is possible 
that you will be able to find the right hardware and software to meet your needs without 
using TAPI services at all. The only drawback is that you'll be using a proprietary system 
that may (or may not) become obsolete in the future. If it is possible, it is a good idea 
to use TAPI-compliant products since the power of Microsoft and the Windows operating 
system is likely to support interfaces like TAPI for quite some time. </p>

<p>Telephony cards (along with TAPI drivers to match) offer the greatest access to TAPI 
services. You can support all the Assisted TAPI and Basic TAPI functions along with access 
to Supplemental TAPI services. Also, if the driver supports it, you will be able to use 
Extended TAPI services to gain access to vendor-specific functions unique to the installed 
hardware. Figure 25.3 shows how telephony cards support all levels of TAPI services. </p>

<p><a HREF="f25-3.gif"><b>Figure 25.3 : </b><i>Telephony cards can support all levels of 
TAPI services </i></a></p>

<h2><a NAME="Summary"><font SIZE="5" COLOR="#FF0000">Summary</font></a> </h2>

<p>In this chapter you learned the differences between the three types of hardware options 
and how they rate in offering support for TAPI services on pc workstations: 

<ul>
  <li><i>Basic data modems</i> support Assisted Telephony services (outbound dialing) and can 
    support only limited inbound call handling. Use this type of hardware if you are building 
    simple outbound dialing applications. </li>
  <li><i>Voice-data modems</i> are capable of supporting the Assisted Telephony and Basic 
    Telephony services and many of the Supplemental services. Use this type of hardware if you 
    want to provide both inbound and outbound services on a single-line phone. </li>
  <li><i>Telephony cards</i> 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 make them ideal for supporting commercial-grade 
    telephony applications. </li>
</ul>

<p>You also got a quick review of modems and modem drivers. You learned that Win95 and 
WinNT rely on the UniModem or UniModemV modem drivers to communicate between the telephony 
hardware and your program. You also learned that, no matter what hardware you purchase, 
you will need a TAPI-compliant <i>TSPI</i> (<i>Telephony Service Provider Interface</i>) 
that matches the hardware you purchased. Hardware vendors may recognize the UniModem or 
UniModemV drivers, or ship their own TSPI drivers with their hardware. </p>

<p>In the next chapter, you'll learn how to use Visual Basic and a special custom OCX 
control to gain direct access TAPI services for your Visual Basic programs. </p>

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