The LINEBEARERMODE_ bit-flag constants describe different bearer modes of a
call. When an application makes a call, it can request a specific bearer mode.
These modes are used to select a certain quality of service for the requested
connection from the underlying telephone network. Bearer modes available on a
given line are a device capability of the line.
This is a regular 3.1 kHz analog voice-grade bearer service. Bit integrity is
not assured. Voice can support fax and modem media modes.
This corresponds to G.711 speech transmission on the call. The network may use
processing techniques such as analog transmission, echo cancellation, and
compression/decompression. Bit integrity is not assured. Speech is not intended to
support fax and modem media modes.
The multiuse mode defined by ISDN.
The unrestricted data transfer on the call. The data rate is specified
The alternate transfer of speech or unrestricted data on the same call (ISDN).
This corresponds to a non-call-associated signaling connection from the
application to the service provider or switch (treated as a media stream by TAPI).
When a call is active in LINEBEARERMODE_PASSTHROUGH, the service provider
gives direct access to the attached hardware for control by the application. This
mode is used primarily by applications desiring temporary direct control over
asynchronous modems, accessed through the Win32 comm functions, for the purpose
of configuring or using special features not otherwise supported by the service
Bearer service for digital data in which only the low-order seven bits of each
octet may contain user data (for example, for Switched 56kbit/s service).
The high-order 16 bits can be assigned for device-specific extensions. The
low-order 16 bits are reserved.
Note that bearer mode and media mode are different notions. The bearer mode of
a call is an indication of the quality of the telephone connection as provided
primarily by the network. The media mode of a call is an indication of the
type of information stream that is exchanged over that call. Group 3 fax or data
modem are media modes that use a call with a 3.1 kHz voice bearer mode.
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