How-to

Exotel integration

Integrate Exotel for India-focused telephony with applet-based call routing, native bridge transfers, and μ-law audio streaming.

Prerequisites

Exotel account — Sign up at exotel.com and obtain your API Key, API Token, and Account SID.
Exotel numbers — Purchase Indian virtual numbers with voice capability.
Passthru applet — Create a passthru applet in your Exotel dashboard that forwards calls to your answer webhook.
Register numbers — Add your Exotel numbers via the Numbers API with provider: "exotel".

India-Focused Provider

Exotel is primarily designed for Indian telephony infrastructure. It offers excellent connectivity, local number support, and compliance with Indian telecom regulations (TRAI).

Environment Variable	Description
`EXOTEL_API_KEY`	Exotel API key for authentication
`EXOTEL_API_TOKEN`	Exotel API token for authentication
`EXOTEL_SID`	Exotel account SID
`EXOTEL_TEMPLATE_APPLET_APP_ID`	Default applet ID for call routing

Applet-Based routing

Unlike Twilio and Plivo which use URL-based webhooks directly, Exotel uses an applet-based routing model.

Trigger Applet API

Exotel Routes via Applet

Customer Answers

Applet Hits Webhook

WebSocket Audio

Voice Pipeline

Passthru Applet Setup

Log in to the Exotel dashboard and navigate to App Bazaar → My Apps
Create a new Passthru Applet and configure the webhook URL to your server’s /exotel/answer endpoint
Note the Applet App ID for the EXOTEL_TEMPLATE_APPLET_APP_ID environment variable
For warm transfer, configure an additional passthru applet for the /exotel/dial-up endpoint

Applet ID Configuration

Source	Setting	Description
Environment	`EXOTEL_TEMPLATE_APPLET_APP_ID`	Default applet ID
Template	`telephony_config.applet_app_id`	Per-template override — takes precedence

Audio encoding

Parameter	Value
Encoding	μ-law (G.711)
Sample Rate	8000 Hz
Channels	Mono
Frame format	Base64 in JSON

Callbacks

POST /exotel/callback/status Call status updates — triggers retry logic for failed calls and updates lead status.

Simplified Callbacks

Exotel uses a single status callback endpoint. Recording URLs are retrieved via the Exotel API after the status callback confirms the call has ended.

Warm transfer

Exotel warm transfer follows a unique pattern where the AI disconnects first:

AI triggers transfer

AI disconnects

Applet calls /dial-up

Returns phone number

Exotel native bridge

POST /exotel/dial-up Called by the Exotel applet after AI disconnects. Returns the transfer target number as plain text.

AI Disconnects First

In the Exotel flow, the AI disconnects before the customer is bridged to the live agent. There is a brief hold period while the applet completes the bridge.

Regional considerations

Consideration	Details
TRAI Compliance	Outbound calls must comply with DND regulations. Exotel handles DND filtering automatically.
Calling Hours	TRAI restricts promotional calls to 9 AM – 9 PM IST.
Number Formats	Indian numbers must include `+91` and 10-digit mobile number.
Latency	Deploy your server in `ap-south-1` (Mumbai) for optimal audio latency.
Language Support	Configure STT/TTS for Indian languages using compatible providers.

Production Applet Configuration

Always verify your passthru applet webhook URLs point to the correct production endpoints before going live. An incorrectly configured applet will silently drop calls.

Next steps

Inbound calls Route incoming calls with IVR.Warm transfer Hand off to a human agent mid-call.Webhooks Receive call lifecycle events.Voice pipeline Tune STT, TTS, and VAD for phone calls.

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