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Frequently Asked Questions

Common questions from teams connecting a PBX, SBC or voice AI stack to SF Trunk, especially teams coming from another SIP trunking provider.

Do I need to allowlist your IP addresses?​

Only if your firewall or platform accepts SIP from known addresses only. Many voice AI platforms route inbound calls by the dialled number and accept SIP from any address. In that case you need nothing.

If you do filter by source address, allow the signalling and media addresses listed in Network addresses to allowlist.

Is my traffic authenticated?​

Your trunk FQDN, <label>.sft.superfone.co.in, identifies your trunk, together with the numbers attached to it:

  • Anyone who knows your FQDN and one of your attached numbers can send calls on your trunk.
  • Every call needs a positive wallet balance to start.

Treat your FQDN like a password.

Can I send calls anywhere?​

Indian phone numbers only. See Outbound calls.

Which codecs can I use?​

G.711 A-law (PCMA) and G.711 µ-law (PCMU). We do not transcode. Always include PCMA in your offer, and do not offer PCMU on its own. See Supported codecs.

Can I use my existing number?​

Yes, if it is a Superfone number in service on your account. Attach it to your trunk. A number can be on one trunk or one SFVoPI app at a time. If it is already on another trunk or an SFVoPI app, attaching it returns an error that names the conflict. Detach it there first.

Only Superfone numbers can be attached. A number from another provider cannot be used with SF Trunk.

Can I have more than one number on a trunk?​

Yes. Attach as many of your numbers as you need. They all share the trunk's limits and your organisation's limits.

What happens if my PBX is down?​

We try your fallback, if you set one. Otherwise the call ends. We always deliver to your primary server first. If it does not respond within about 5 seconds, or replies with a 5xx error, we try your fallback once. If your primary rang and nobody answered, or it rejected the call, we do not try the fallback and the call ends. Unanswered calls ring for up to 60 seconds in total. See Fallback destination.

Can I transfer a call to the Superfone app?​

Yes, for incoming calls, with a SIP REFER from your PBX. Refer the call to the phone number of a Superfone user in your organisation, and add an optional X-SF-TR header with a reason that the agent sees in the app. If the agent does not answer, the call ends. See Call transfer to Superfone app.

What happens when my wallet reaches Rs. 200?​

New calls are refused, in both directions. We check the balance when each call starts. Calls already in progress keep going until they end but you need to have at least Rs. 200 in your Wallet to make or receive new calls. Top up your wallet to start taking calls again. See Limits and billing.

How do I raise my CPS or concurrent-call limit?​

Org-limits release

Organisation call limits, and trunk limits you can set, ship with the org-limits release.

Email hello@superfone.in. Superfone sets your organisation's limits to match the capacity you bought. You cannot raise them yourself.

You can set a lower limit for one trunk with Update a trunk. It cannot be higher than your organisation's. See Capacity limits.

Are trunk calls recorded?​

Yes, if recording is turned on. Each trunk has its own call recording setting, and it applies in both directions. By default it is not set, and calls follow the call recording setting of the Superfone number on the call. Turn it on or off on the trunk to override the number's setting. The setting is per trunk, not per number. See Limits and billing.

Is there a maximum call length?​

Yes. A trunk call can last up to one hour.

Can my PBX register to SF Trunk?​

No. SF Trunk does not accept REGISTER. Set up your trunk as a static peer pointing at your trunk FQDN.

Next Steps​