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The term convergence is usually applied to the integration of voice and data services on the same network, either in the enterprise or over public networks such as the Internet. CTI is the integration of telephony services with computers, servers, PBX devices, and other computer-related equipment. These two areas are merging as organizations install high-speed networks that can carry both voice and data.

Although the first implementations of CTI integrated computers with the circuit-switched voice phone network, new CTI products operate over IP data networks. A range of devices is possible, including:

• At the low end, a diskless device that integrates a Web browser and telephone functionality.


• At the high end, a desktop computer with telephone, videoconferencing, speech recognition, and just about anything else you might use in a telephony environment such as automatic answering, call forwarding, voice messaging, and so on.

IVR (Interactive Voice Response) is a CTI application. It is the front-end "computerized operator" that guides you through button-pushing options when you call a company (i.e., "press 1 for sales, press 2 for service"). Putting this on computers has simplified setup for administrators because an easy-to-use interface makes it easy to program selections and add or change a message. It is even possible to have messages change automatically based on programmed times or dates.

Universal in-box is another aspect of CTI. It can provide services such as voice mail, faxing, and e-mail on a company-wide basis. Information is stored on disk and accessible to users who dial into the server from their phone, or access it from their workstation. In the latter case, voice messages travel across the network to the recipient's computer where they are played back, so this is getting close to voice networking. However, stored messages are not real-time voice, so bandwidth requirements are not as strict. This is one of the biggest concerns with integrating voice over networks. The voice calls are live, and if enough bandwidth is not available, the conversation becomes garbled.

To provide a basis for CTI, Novell created TSAPI (Telephony Services API) and Microsoft created TAPI (Telephony API). TSAPI was enhanced in 1996 by a vendor consortium called Versit, which includes IBM, Siemens, and Apple Computer as its members.

Note, however, that these protocols do not combine voice and data networking. They allow a computer to manipulate telephone devices that are connected to telephone lines. In some cases, telephony devices might be connected over a network, but the signals that cross the network are for control. They are not voice signals.

Applications can use TSAPI or TAPI to interact with devices like phones, PBXs, and modems. Microsoft Windows uses TAPI in a number of built-in applications to interact with modems. For example, a phone dialer program lets you enter names and phone numbers in a notepad that can be selected and dialed at any time. Windows can do a number of other things as well using TAPI, like answer incoming phone calls and faxes, forward calls, and provide voice mail. A fax application is included that receives incoming faxes and displays them in a graphical interface where they can be manipulated as if working in a drawing program.

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
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