Two kinds of applications are needed to run Assisted Telephony. Assisted Telephony clients are applications that use Assisted Telephony by calling the functions that have the prefix "tapi." An example of such a client application would be a spreadsheet to which a Dial menu command or toolbar button is added.
Assisted Telephony servers are applications that can execute Telephony API functions that result from another application's call to a "tapi"-prefixed function. To make itself known as an Assisted Telephony server, such an application registers as one using the lineRegisterRequestRecipient function.
The functions of Assisted Telephony (which begin with the prefix "tapi") are known as request functions. Assisted Telephony applications that process these requests—Assisted Telephony servers—are called request recipients.