Obtaining a Line
Next, the application needs to obtain a handle to a capable telephone line.
The application opens the line with lineOpen
, but before doing this, it must make sure that the line can support the
desired type of call. Invoking the lineGetDevCaps
function returns that information to the application in a data structure of
. If data calls were not supported, this fact could be reported to the user in
a dialog box. The application does not need to use lineGetDevCaps
before every call, because a line's capabilities should remain static. If the
local telephonic configuration (as expressed in .INI files) changes, TAPI
notifies applications, which can then call lineGetDevCaps
to see what has changed.
One of the values returned by lineGetDevCaps
(as a field in the LINEDEVCAPS
structure) is the number of addresses assigned to the specified line device.
In this example, a single device has a single address.
Ownership of a call is a type of privilege. Applications obtain owner or
monitor privilege to new incoming calls by specifying the desired privilege as a
parameter of lineOpen
. The privilege with which a line is opened remains in effect for subsequent
calls used by that application on that line. An application always has owner
privileges on calls it creates. When the application opens a line to place calls
(as opposed to taking inbound calls) it invokes lineOpen
with the privilege LINECALLPRIVILEGE_NONE, which insulates the application
from incoming calls while allowing outgoing calls. The other privileges used with
function are only for incoming calls.
The LINEOPENOPTION_SINGLEADDRESS option is available when using the lineOpen
function to allow the application to specify that handles for new calls
(either monitor or owner handles) should be delivered to the application only if the
address on which the call appears matches the address provided as a function
parameter. This is extremely useful when different addresses on a line are
designated for calls of different media modes.
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