function enables service providers to provide access to features not offered
by other TAPI functions. The meaning of these extensions are device specific,
and taking advantage of these extensions requires the application to be fully
aware of them.
| HLINE hLine,
| DWORD dwFeature,
| LPVOID lpParams,
| DWORD dwSize
A handle to the line device.
The feature to invoke on the line device. This parameter uses the
A pointer to a memory area used to hold a feature-dependent parameter block.
The format of this parameter block is device specific and its contents are
passed through by TAPI to or from the service provider.
The size of the buffer in bytes.
Returns a positive request ID if the function will be completed
asynchronously, or a negative error number if an error has occurred. The dwParam2
parameter of the corresponding LINE_REPLY
message is zero if the function is successful or it is a negative error
number if an error has occurred. Possible return values are:
LINEERR_INVALFEATURE, LINEERR_OPERATIONUNAVAIL, LINEERR_INVALLINEHANDLE,
LINEERR_OPERATIONFAILED, LINEERR_INVALPOINTER, LINEERR_RESOURCEUNAVAIL,
Additional return values are device specific.
This operation is part of the Extended Telephony services. It provides access
to a device-specific feature without defining its meaning. This operation is
only available if the application has successfully negotiated a device-specific
This function provides the application with phone feature-button emulation
capabilities. When an application invokes this operation, it specifies the
equivalent of a button-press event. This method of invoking features is device
dependent, as TAPI does not define their meaning. Note that an application that relies
on these device-specific extensions will typically not work with other service
Note also that the structure pointed to by lpParams
should not contain any pointers because they would not be properly translated
(thunked) when running a 16-bit application in a 32-bit version of TAPI and
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