Basic Telephony Services are a minimal subset of the Win32 Telephony specification. Because all service providers must support the functions of Basic Telephony Services, applications that use only these functions will work with any TAPI service provider. The functionality contained in Basic Telephony roughly corresponds to the features of POTS.
Today, many programmers will use only the services provided by Basic Telephony. But others, such as those writing code for PBX phone systems, will need the functions of Supplementary Telephony. Soon, the demand for ISDN and other network services, along with advancements in telephone equipment, will drive even greater usage of Supplementary Telephony.
For a list of the functions of Basic Telephony, see TAPI Quick Function Reference.
Because control of phone devices is not assumed to be offered by all service providers, phone-device services are considered to be optional. That is, they are not a part of Basic Telephony. For a list of phone-device services, see Supplementary Telephony Services; for more information on phone devices, see TAPI Device Classes.