The SBC supports Text over Internet Protocol (ToIP), including the inter-working between ToIP and the Text Telephone (TTY) protocols employed in Code Division Multiple Access (CDMA) wireless networks and wire-line VoIP networks (using Baudot).

The support is applicable for SBC deployments in virtual and cloud environments (I-SBC and D-SBC).

The following interworkings and related transcodings are supported:

Supported Interworkings and Transcoding

InterworkingTranscoding

T.140 to TTY

  • AMR-NB to EVRC/EVRC-B
  • AMR-WB to EVRC/EVRC-B
T.140 to Baudot
  • AMR-NB to G711A/U
  • AMR-WB to G711A/U
TTY to Baudot supportEVRC/EVRC-B to G711

Note
  • The SBC supports pass-through for all the text transmission protocols mentioned above.
  • The SBC performs T.140 to TTY/Baudot Interworking only when the call is transcoded. However, the SBC does not add DSP/transcoding resource just to perform this interworking.
  • The SBC does not voluntarily insert a "m=text" line, even though the t140Call flag is enabled on the egress trunk group. The SBC only relays the "m=text line", or interworks with TTY/Baudot, if the ingress SDP contains a valid "m=text" line.
Note

The following limitations apply:

  • Ribbon supports only 45.45 bps Baudot.
  • Maximum buffering for T.140 packets is approximately 30 seconds.
Note

To configure this feature, ensure that the t140Call parameter is set to enable, by using the following syntax:

% set profiles media packetServiceProfile <profile_name> flags t140Call enable

RTCP Generation For T.140 Pass-Through Calls

Based on PSP configuration, the SBC has the capability to generate RTCP for T.140 pass-through media streams if RTCP is not received from other peer. The interval for which the SBC monitors the RTCP packets for T140 stream from endpoints are also defined. If RTCP is not received within the interval, the SBC starts RTCP generation. 

For more information, refer to Packet Service Profile - CLI.