The number of TAPI-compatible products on the market continues to grow, supporting a broad range of telephone networks and applications. There is a wide spectrum of applications developers, both established companies and start-ups, coming from both the PC and telecommunications heritage. Every major PBX vendor in the world is shipping or has under development TAPI drivers for their systems. In addition to the PBX, drivers are available for the analog PSTN, ISDN, Centrex, client/server telephony, and even cellular.
Literally hundreds of thousands of developers worldwide have the ability to write TAPI solutions and they can receive the TAPI software developers toolkit and related documentation via their subscriptions to the Microsoft Developer Network. Because Microsoft does not require that each developer register its TAPI compatible product, it is difficult to gauge the precise number of TAPI products available. That being said, there are a some product listings and directories available in print, via the Internet, and referenced in market studies which capture at least some of the momentum and solution activity. You can find links to some of the companies offering TAPI-based products under the telephony solutions area on the Microsoft Web site for network communications and telephony at http://www.microsoft.com/communications.