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Call transfer to Superfone app

Your PBX can hand an incoming call on your trunk, one a caller placed to your Superfone number, to a user of the Superfone app. The agent's app rings, and if they answer, the caller talks to them.

This transfer reaches only users of the Superfone app in your own organisation. To send a call to any other number, see Transferring to any other number.

Send the transfer​

Send a SIP REFER on the call, with a Refer-To that points at the phone number of the Superfone user, in E.164 format with a leading +:

Refer-To: <sip:+91XXXXXXXXXX@your-trunk-fqdn>
X-SF-TR: Caller wants to upgrade their plan
TargetThe phone number of a Superfone user in the same organisation as your trunk. Other numbers cannot be reached
Number seriesThe agent's Superfone number must be in the same number series as the number the call came in on
X-SF-TR headerOptional. Free text that is shown to the agent in the app while the call rings. Keep it short. Anything over 256 bytes is truncated
Ring timeThe agent's app rings for about 20 seconds

Most PBXs have a "blind" or "unattended" transfer action that sends the REFER. Check your PBX documentation for how to add a custom header to it.

When the transfer does not succeed​

If the agent does not answer, declines, or their app cannot be reached, the call ends. We do not hand the call back to your PBX. If the number in the REFER is not the number of a Superfone user in your organisation, the call also ends.

Transfer works only when the agent's Superfone number is in the same number series as the number the call came in on. If it is in a different series, the agent's app does not ring and the call ends straight away. The transfer is logged as failed in your call history.

Your PBX cannot see these failures in SIP. We accept every REFER with 202 Accepted and confirm it with a NOTIFY of 200 OK before the agent's app rings. Your PBX's leg then leaves the call. Check the call history for the result.

Check the number before you transfer

Keep the numbers of your Superfone agents in your PBX configuration and transfer only to those.

Transferring to any other number​

Superfone does not transfer a call to an arbitrary phone number. If you need that, build it in your PBX with the bridge method:

  1. Keep the first call up. Put the caller on hold or play music to them if you want.
  2. Place a second call from your PBX to the target number over your trunk. See Outbound calls.
  3. When the second call is answered, bridge the two calls in your PBX so the caller and the person who answered hear each other.

Both calls go through your trunk, so each one counts as a separate call for billing and limits. Your PBX ends both calls when the conversation is over.

Next steps​