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5. ISDN Function Reference
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5.2. Programming Conventions
The Dialogic ISDN library functions use the following format:
cc_function(reference, parameter1, parameter2, parameterN, mode)
Where:
• cc_function is the function name
• reference is an input field that directs the function to a specific line device or
call when the reference is a CRN or a line device handle (see Section
5.3. Function References: CRNs, CRVs, and Line Device Handles below for
more information)
• parameter1, parameter2, parameterN are input fields
• mode is an input field indicating how the function is executed. Set the value
to EV_ASYNC for asynchronous mode execution or EV_SYNC for
synchronous mode execution.
5.3. Function References: CRNs, CRVs, and Line Device
Handles
Most functions ask for the line device handle and/or the call reference number
(CRN), which together enable applications to be written independent of the
hardware type or signaling protocol.
The line device handle is a unique logical number assigned to a specific device or
device group by the ISDN API. The line device handle enables the API function
to address any system resource using a single device identifier. The system
architecture also permits more than one device to be addressed as a unit, as
needed to process a call.
A call reference number (CRN) identifies a call on a specific line device. The
CRN is created by the ISDN API library when a call is requested either by the
application or the network. The relationship between the CRN and a line device is
established when a call is requested and acknowledged by the other end. The valid
lifespan of the CRN is the duration of the call. Afterward, the CRN can be
reassigned.