How to correctly manage In-band Media and Play Ringback on Sonus SBC with SfB and Teams

Hi All,

recently I managed an interesting Customer’s issue, maybe the solution could help some of you.

A Sonus SBC 1000 (FW Ver 7.0.2 build 485) is connected to:

  • Skype for Business On-Prem (UC Signaling Group)
  • Microsoft Teams via Direct Routing (TEAMS Signaling Group)
  • analog devices connected on onboard FXS ports (FXS Signaling Group)
  • the Carrier via E1 ISDN (PSTN Signaling Group)

Customer tell us that if they call a particular toll-free phone number (in this example 800123456) from Skype for Business, they do not ear any welcome audio message, only ringing for few minutes, then call drop.
The issue was the same also if you try to call the toll-free number from Microsoft Teams.

If they call the same number from an analog line connected to the same Sonus SBC, they can ear the audio message and correctly go on on call.

This is clearly a In-band Media configuration issue.

In-band Media and In-Band Audio Messages
In-band Media is widely used in Telephony Services and Call Center to send audio messages to callers even BEFORE che call is established.
This very useful feature is used to inform that the called number is wrong, or the mobile phone is disconnected of out of range, to leave a message in the voice mail or the price fare for the called service (Premium services).

Signaling Groups correct setup
If you have this issue, and to solve it, you have to change the “Play Ringback” setting in your Signaling Groups, from Always to Auto

SIP Signaling Groups (UC and Teams in this scenario)
Set Play Ringback to Auto on 180/183
I assume Early 183 is Enabled, becaus it’s mandatory with SfB/Teams

ISDN Signaling Group
Set Play Ringback to Auto on Alert/Progressinband04

CAS Signaling Group
Set Play Ringback to Autoinband05

With this configuration the caller could ear any In-Band message (if present), from Skype for Business and Microsoft Teams clients
Another happy customer with a Sonus SBC and Microsoft UC solution 🙂

Sonus Documentation
On that page of the always good Sonus SBC online documentation you can find more info about Play Ringback settings:

Best Regards


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