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Integrating Fin Voice with your telephony system using call forwarding

Use this guide to connect Fin Voice with your existing telephony system using universal PSTN call forwarding.

Dawn avatar
Written by Dawn
Updated over a week ago

The fastest way to get Fin Voice live and integrated with your existing phone system is by using PSTN (Public Switched Telephone Network) call forwarding. This method works universally with any telephony provider and is the recommended entry point for pilots and early deployments.

What is Fin Voice?

Fin Voice is Intercom’s AI Agent for phone support. It answers calls instantly, resolves questions using your help content, and can seamlessly hand off the call to a human teammate with full context when needed.

Fin Voice is designed to integrate with any existing telephony provider, allowing you to keep your current phone system while adding powerful AI-powered support.

How the integration works

This setup uses standard PSTN forwarding to route incoming calls from your telephony provider to a dedicated Intercom number for Fin Voice. It does not require SIP (Session Initiation Protocol), which is why it is universally supported.

You can migrate to a cheaper, more robust SIP-based deployment later if your provider supports it.

Why we recommend PSTN for trials

PSTN forwarding is the recommended entry point for pilots and early-stage deployments for two main reasons:

  1. It is the fastest way to get customers live.

  2. It is universally supported by every platform and requires minimal setup.

Setting up the Fin Voice call flow

Prerequisites

To set up this integration, you'll need the following:

Requirement

Description

Intercom workspace

Fin Voice must be enabled and hosted in the US, EU, or AU region.

Intercom admin access

Permissions are required to set up and manage Fin Voice.

Knowledge base

Fin needs access to rich, up-to-date support content.

Telephony admin access

Ability to edit call routing or forwarding rules in your external provider.

External phone number

Active inbound numbers on your telephony provider.

Optional: IVR workflow with HTTP request capability

Required only if you want to use the Fin Voice API to pass summaries, transcripts, and intent to your agents. Your provider must support making HTTP requests from an IVR or call routing workflows.

1. Test Fin Voice

You can simulate calls in-browser using the Voice testing tab before involving any real customers.

  1. Go to Fin AI Agent > Deploy > Phone > Voice testing.

  2. Click Test.

  3. Wait for Fin to greet you, and then begin speaking normally. Allow your browser access to your microphone if prompted.

Tip: This test allows you to hear Fin answer using your own support content, switch voices, and preview greetings and escalation rules exactly as callers would hear them.

2. Create a Fin Voice line

When you're ready to set up a live phone line, you'll purchase a number from Intercom that your provider will forward calls to.

  1. Navigate to Fin AI Agent > Deploy > Phone > Set Fin Live.

  2. Click New line.

  3. Select External provider and hit Next.

  4. Give the line a name (e.g., "Fin Voice").

  5. Under 'Where will you forward calls from?', select From a phone number (PSTN), then choose Next.

  6. Select Purchase to acquire a US local phone number provided through Intercom Phone.

Note: When calls are forwarded over PSTN, Intercom Phone usage charges apply. These charges include a monthly fee for the US local number, and inbound/outbound per-minute charges. These are separate from Fin Voice's per-resolution pricing.

3. Configure Fin’s behavior

You can customize how Fin operates before integrating with your telephony provider.

  1. Open the line you just created in Fin AI Agent > Deploy > Phone > Set Fin Live.

  2. Review and adjust these optional settings:

    • Office hours: Choose when Fin should answer calls (defaults to 24/7).

    • Voice, language, and greetings: Select Fin's voice, language, and customize the greeting.

    • Audiences: Restrict which support content Fin can use by targeting specific callers or phone numbers.

    • Guidance: Set rules for Fin's communication style and when it should escalate.

    • Category Detection: Enable AI-based topic classification for routing or reporting.

    • CSAT: Enable keypad ratings (1–5) for resolved calls.

Enable recordings and transcripts

To review customer interactions and see how Fin handled each call, enable recordings and transcripts.

Note: This is a global setting for all Phone calls. It's not possible to only enable recordings or transcripts for some calls.

4. Forward calls to Fin Voice

In your telephony provider's routing or IVR editor, forward incoming calls to the Intercom number you purchased.

The flowchart showing the initial transfer from the IVR to Fin.

5. Configure Handovers Back to Your Provider

Set up a way for Fin to transfer the call back to your human team when it can't resolve a question.

  1. Create a dedicated escalation number in your telephony provider. This number should route callers to your team's call queue.

  2. In Intercom, go to Fin AI Agent > Deploy > Phone > Set Fin Live.

  3. Under 'If Fin can’t resolve the conversation', select Forward the call and enter the escalation number you created in your provider.

  4. Select the option to Close the conversation when the call is forwarded.

The flowchart showing the transfer back from Fin to the Call Queue.

Add context to handovers using the Fin Voice API

For a smoother agent experience, you can pass Fin's summary, transcript, and intent to your agents via the Fin Voice API's Call object. This optional step is useful when your telephony provider supports making HTTP requests within its IVR or call routing workflow.

1. Get an API access token

  1. Open the Intercom Developer Hub and select New app.

  2. Enter a name (e.g., "Fin Voice Connector") and select the correct workspace, then Create app.

  3. Copy the Access token from the Authentication page. You'll use this as the Bearer token for API requests.

2. Register the call

In your provider's call flow, use an HTTP request to call the /register endpoint before forwarding the call to Fin.

  • Action: Before the call is forwarded to Fin, call the Voice API - /register endpoint.

  • Endpoint: POST https://api.intercom.io/fin_voice/register.

  • Parameters: Include the caller’s phone_number (in E.164 format) and your provider’s unique call_id.

Note: The call must be registered before you call /collect. If you register after forwarding, it must happen within 2 minutes of Fin receiving the call.

The flowcharts showing the /register and /phone_number API calls.

3. Retrieve call data on handover

After Fin forwards the call back to your provider, you must retrieve the call summary, transcript, and intent using the caller’s phone number.

The example below shows the high-level routing flow. Your provider's IVR or routing editor will look different.

  • Step 1: Get Intercom call ID: Call Voice API - /phone_number using the caller's number. This endpoint returns Intercom’s internal call ID in the id field.

  • Step 2: Collect context: Call Voice API - /collect using the Intercom call ID obtained in Step 1.

    • This returns the call_transcript, call_summary, status, and intent.

You can then use this data to populate your provider’s inbound call notification, giving agents the context they need before they pick up the escalated call.

💡Tip

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