Non-exclusive mode (preferred mode)

When a TCP instance places a call in non-exclusive mode, it requests the use of its default channel from the network. The network allows the use of the default channel or directs the TCP to use a different channel. If a different channel is assigned, the application must perform switching to route the call to the DSP resource associated with the TCP instance.

To do so, the application must:

For example, if a TCP attempts to establish an outbound call on its default B channel, the default channel is 5, corresponding to MVIP-95 0:4,1:4. The network indicates that channel 5 is not available, but channel 9 is available (corresponding to MVIP-95 0:8,1:8). Since the TCP is running in non-exclusive mode, the call is established on channel 9. The application must now connect the TCP instance's DSP resource (MVIP-95 16:4, 17:4) with the B channel to establish the voice path (for example: 0:8 => 17:4, 16:4 => 1:8). In MVIP-90 terms, this connection is 16:8 <=> 18:4.

Incoming calls from any B channel are routed to the TCP instance unless the B channel on which the call is located is assigned to another TCP running in exclusive mode. For details, see Switching considerations for disconnect handling.

To set a TCP instance to exclusive mode, set the NCC.ADI_ISDN.START_EXT.exclusive parameter to 1.

Switching considerations for disconnect handling

In non-exclusive mode, when a call is disconnected the application must disconnect only the trunk-to-DSP side of the full duplex switching connection that it made when the call was established. The DSP-to-trunk connection must not be disconnected because it may interfere with a new call arriving on the B channel that is handled by another thread or process.

Disconnecting the trunk-to-DSP connection ensures that if a new outgoing call is placed on the context, any call progress analysis functions receive only silence until the application makes a new connection.