Enabling the R2 Protocol

R2 Call Control

This section presents an overview of R2 outbound and inbound call setup and tear down. LEC protocols and ISDN use a similar mechanism.

Once the trunk is configured, a particular channel that is enabled is ready to dial an outbound call or process an inbound call from the network. The R2 protocol stack automatically selects a DSP channel (Boston channel) to perform the tone detection/generation operations. The first B-channel on the first line uses the first DSP channel, then each subsequent B-channel selects the next DSP channel.

The first B-channel on the next line selects the DSP channel immediately following the DSP channel selected for the last B-channel of the previous line, thus ensuring there are no gaps in the DSP channel usage caused by different number of timeslots in T1 and E1 lines.

During call setup - either inbound or outbound - the application must not issue any commands to the Tone Generation and Tone Detection facilities, as these would interfere with the R2 signaling and cause the call to be abnormally terminated. If the application connecting DSP channels and B-channels through the Telephony Bus (H.100), it must ensure the appropriate DSP channel is free and connected to the corresponding B-channel when it is ready to receive/place calls. Once the call is connected, the DSP and B-channels are remapped.

November 2009

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Dialogic 6.2 manual R2 Call Control, November 355