1.5.2 Call Reference Number

A Call Reference Number (CRN) is a means of identifying a call on a specific line device. A CRN is created by the Global Call library when a call is requested by the application, thread or network.

With the CRN approach, the application (or thread) can access and control the call without any reference to a specific physical port or line device. CRNs are assigned to both inbound and outbound calls:

Inbound calls

The CRN is assigned via the gc_WaitCall( ) function. For more information on gc_WaitCall( ), see the Global Call API Library Reference.

Outbound calls

The CRN is assigned via either the gc_MakeCall( ) or gc_SetUpTransfer( ) function. For more information on these functions, see the Global Call API Library Reference.

This CRN has a single LDID associated with it, for example, the line device on which the call was made. However, a single line device may have multiple CRNs associated with it (that is, more than one call may exist on a given line). A line device can have a maximum of 20 CRNs associated with it. At any given instant, each CRN is a unique number within a process. After a call is terminated and the gc_ReleaseCallEx( ) function is called to release the resources used for the call, the CRN is no longer valid.

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