In E-1 CAS and T-1 robbed bit protocols, a combination of line signaling and audio tones are used to establish a call. The line signaling is controlled by a network time slot device, or resource, and the tones are controlled by a voice channel (voice resource). Voice channel, voice resource, and tone resource are used interchangeably in this manual when discussing Global Call functionality.
Typically, in E-1 CAS or T-1 robbed bit environments, a Global Call line device consists of a network time slot resource and a voice resource. When the same voice resource is always used for a given network time slot, then this configuration is called a dedicated voice resource. The Global Call line device ID is a single ID that represents the combination of the voice and network resources that work together to establish and to tear-down calls.
In configurations with more network time slot resources than available voice (or tone) resources, the application may share these available voice resources among the time slots (resource sharing). When voice resources are shared, the Global Call line device ID represents a network time slot after issuing a gc_OpenEx( ) function. However, before issuing a gc_MakeCall( ) or a gc_WaitCall( ) function, a voice resource must be attached to the Global Call line device using the gc_Attach( ) function and then routed to the line device's network time slot. The gc_Attach( ) function tells the Global Call protocol handler which voice channel will be used to establish the call. Once the call is established (answered), the application can use this voice resource for other calls by first detaching the voice resource using the gc_Detach( ) function from the current line device and then attaching this voice resource to another line device using the gc_Attach( ) function. The gc_Detach( ) function must not be used to detach the voice resource until the call is in the connected state. See Section 5.1. Dedicated Voice Resources and Section 5.2. Shared Voice Resources for more information.
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