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Sinch

Answer calls to your Sinch numbers with your receptionist over a SIP trunk.

Sinch forwards calls to Reception.ai over a SIP trunk. Your numbers stay on Sinch, and Sinch bills you for the minutes. Sinch uses one Voice app to send calls to Reception.ai and a second app to carry transfers back out.

Before you start

  • A Sinch account with at least one phone number.
  • Sinch’s SIP signaling IP ranges for your region, listed under IP allowlisting in Sinch’s documentation. Reception.ai only accepts calls from addresses you allow.

Setup

1

Add the SIP trunk in Reception.ai

Go to Integrations, select Add integration, and choose SIP Trunk. Under Inbound allowed addresses, add Sinch’s SIP signaling ranges for the regions you use. Leave the inbound username and password empty; Sinch’s SIP forwarding doesn’t send credentials.

2

Add the number

Go to Receptionists, select the Phone tile, enter your Sinch number with its country code, and select Add SIP Trunk number. Reception.ai shows the SIP servers and the request URI to use, over TCP or TLS.

3

Forward calls in Sinch

In the Sinch Build Dashboard, go to Voice and Video → Apps and open (or create) the app your number belongs to. Under Settings, set Handle call events with to SIP Forwarding and enter a forwarding URI that uses the Reception.ai SIP server, for example:

sip:{number}@SIP_SERVER:5061;transport=tls

Sinch replaces {number} with the number that was called. Use port 5060 with transport=tcp if you prefer TCP. Don’t leave out the transport parameter: Sinch uses UDP by default, which Reception.ai doesn’t accept.

4

Assign your number

Assign your Sinch number to the app that forwards to Reception.ai.

5

Set up transfers

Your receptionist transfers calls by placing a new call through your outbound trunk. In Sinch, create a second app for SIP termination and note its Application Key and Application Secret. In the Reception.ai SIP trunk, set:

SettingValue
Outbound SIP addressYour region’s Sinch termination host, for example use1.vp.sip.sinch.com (North America) or euc1.vp.sip.sinch.com (Europe)
Outbound usernameThe termination app’s Application Key
Outbound passwordThe termination app’s Application Secret
Transport (advanced)TCP

The full list of regional hosts is under Termination URIs in Sinch’s documentation.

6

Test it

Call your Sinch number from another phone and check that your receptionist answers. Then ask to be transferred.

The Application Secret lets anyone place calls billed to your Sinch account. Keep it out of shared documents, and regenerate it in Sinch if it leaks.

Troubleshooting

ProblemWhat to check
Calls fail before ringingCheck that the forwarding URI ends in ;transport=tls or ;transport=tcp and uses the matching port, 5061 or 5060.
Calls are rejectedAdd Sinch’s signaling ranges to Inbound allowed addresses. The request URI must start with the number in E.164 format, for example +14155550123. If Sinch sends it without +, change the forwarding URI to sip:+{number}@….
The receptionist doesn’t answerMake sure the number is added on the receptionist’s Phone tile and assigned to the forwarding app in Sinch.
One-way or no audioSinch offers encrypted media (SRTP) when calls arrive over TLS. Check that Media encryption in the trunk’s advanced settings allows it, or switch to TCP.
Transfers failCheck the outbound host, key and secret, and that the transport is TCP. Sinch only accepts caller IDs that are Sinch numbers or verified in the Build Dashboard.