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11. TAPI in C# and VB.NET
TAPI, or the telephony application-programming interface is
the mechanism by which computers can respond to phone calls. It is the
technology behind call-centres, and all CTI (Computer Telephony Integration)
applications. This application can be used to detect, pick up, and play a
pre-recorded message to callers.
You will need a voice modem to use this application. Data
modems can still be used with this, but you will not be able to send and
receive audio after the call is accepted.
To use the application, ensure that your modem is plugged
into a phone line, then press the ‘Start Modem’ button. With a second phone,
ring the number for the phone line which is connected to your PC’s modem. You
will see “Event: Ringing” appearing on-screen. Press ‘Accept Call’ to accept
the call. At this point, the line is opened (and is probably costing you on
your phone bill). You can then play a sound to the recipient by pressing the
browse button, selecting an audio (.wav / wave) file, and pressing the ‘play
sound’ button. The caller will then hear the sound, -albeit with some degraded
sound quality. You may also receive DTMF (dual tone modulated frequency) keypad
presses, as they appear on-screen as TAPI events. To drop the line, press ‘Stop
modem’.