SIP Trunk Voice AI Integration: Connect Exotel & Twilio to Bolti
Founder of Bolti, writing about voice AI for Indian businesses.
Bolti, a voice AI platform for phone agents, lets you build production-ready conversational agents with sub-second latency and real interruption handling. Whether you are running outbound sales, customer support, or automated QA, you can start building immediately with our 50-minute free trial or scale up with our ₹6/min pay-as-you-go pricing. To make these agents work with your existing telephony infrastructure, you need to configure a SIP trunk voice AI integration.
By routing calls from existing providers like Exotel or Twilio directly to Bolti, you maintain control over your phone numbers, carrier relationships, and call routing logic while leveraging Bolti's advanced voice pipeline.
What is a SIP trunk voice AI integration?
A SIP trunk voice AI integration is the process of connecting a standard Session Initiation Protocol (SIP) trunk from a telecom provider to an AI-powered voice engine.
This connection allows your existing telephony infrastructure to hand off live phone calls to Bolti's runtime. Instead of routing a customer call to a human call center agent, your SIP trunk routes the call to a digital voice agent. This agent can listen, understand, and reply in real time using Bolti's optimized pipeline, which handles:
- Voice Activity Detection (VAD): Pinpointing exactly when a caller starts and stops speaking.
- Turn Detection: Deciding when it is the agent's turn to speak.
- Interruption Handling: Allowing callers to naturally cut off the agent mid-sentence.
- Telephony Noise Cancellation: Stripping out background static and line noise so speech-to-text engines can transcribe accurately.
How do you connect a Twilio SIP trunk to Bolti?
Connecting Twilio to Bolti requires configuring a SIP domain in Twilio and pointing it to Bolti's SIP endpoint, then registering that trunk in your Bolti workspace.
To establish this connection, follow these steps:
- Configure the Twilio Elastic SIP Trunking: Log into your Twilio Console, navigate to Voice > Elastic SIP Trunking, and create a new SIP Trunk.
- Set up the Termination URI: Define your termination URI in Twilio. This is where Twilio will send traffic. Point this to the Bolti SIP termination address provided in your dashboard.
- Configure Origination: Set up the origination URI to route inbound calls from your Twilio numbers to Bolti's SIP URI.
- Register the Trunk in Bolti: In the left navigation of your Bolti dashboard, go to the Phone Numbers page. Under the trunks section, add a new SIP trunk, select "Twilio" as the provider, and enter your SIP trunk details.
- Assign the Number to an Agent: Go to the Phone tab of your specific voice agent. Under "Assign New Number", select your newly configured Twilio trunk, enter the DID phone number in E.164 format (e.g.,
+919876543210), and click Assign Number.
How do you connect an Exotel SIP trunk to Bolti?
Connecting Exotel to Bolti involves setting up an IP-peering or SIP registration session inside the Exotel dashboard and pointing your virtual numbers to Bolti's SIP endpoint.
Because Exotel is a dominant telecom provider in India, this integration is highly optimized for local routing. Follow this sequence to set it up:
- Request SIP Trunking in Exotel: Contact your Exotel account manager or use the Exotel dashboard to enable outbound/inbound SIP trunking on your virtual numbers.
- Configure IP Whitelisting: Add Bolti's production SIP IP addresses to your Exotel whitelisted IPs to allow SIP traffic to flow securely.
- Add the Exotel Trunk to Bolti: Log into your Bolti workspace, navigate to the Phone Numbers page, and add a new SIP trunk. Choose "Exotel" as your provider type and enter your Exotel SIP domain.
- Map the Virtual Number: Go back to your agent's settings, click the Phone tab, select your Exotel trunk, and input your Exotel virtual number in E.164 format starting with
+91.
Once assigned, any incoming call to that Exotel number will bypass traditional IVRs and route instantly to your conversational AI agent.
Why choose a Bring Your Own Carrier (BYOC) model?
Using a BYOC model with your own SIP trunks gives your business complete control over your call routing, carrier costs, and compliance requirements.
While Bolti provides pre-configured phone numbers out of the box, integrating your own Exotel or Twilio SIP trunks offers several key advantages:
| Feature | Bolti Default Numbers | Bring Your Own Carrier (BYOC) |
|---|---|---|
| Carrier Control | Managed by Bolti | Managed by you (Twilio, Exotel, Plivo) |
| Pricing | Included in standard rates | Paid directly to your telecom provider |
| Number Porting | Not required | Keep all your existing business numbers |
| Local Indian Routing | Standard international routing | Optimized local routing via Exotel/local gateways |
| Enterprise Features | Standard workspace limits | Custom SIP configurations and Dedicated IPs |
If you want to talk to our integration engineering team about custom SIP setups, dedicated IP ranges, or on-premises deployment options, we can help you configure complex routing rules.
How does the voice pipeline process SIP calls?
When a call arrives via your SIP trunk, Bolti's runtime immediately spins up a dedicated session for that call, running a low-latency pipeline to process the audio.
This pipeline orchestrates four main steps to ensure natural, human-like conversation:
- STT (Speech-to-Text): The caller's incoming SIP audio stream is transcribed in real time. For Indian-language calls routed through Exotel, you can select specialized STT engines like Fennec or Sarvam in your agent's Speech tab to handle accents and regional dialects.
- LLM (Large Language Model): The text transcript is sent to the brain of the agent (such as OpenAI's GPT models, Gemini, or Groq) along with your system prompt and tools. The LLM decides what to say next or triggers an API call.
- TTS (Text-to-Speech): The text response is converted back into high-quality audio. Through the Voice tab in Bolti, you can select from ultra-realistic voices from ElevenLabs, Cartesia, or Indic-focused voices like Anushka from SarvamAI.
- SIP Audio Return: The synthesized voice is streamed back through the SIP trunk directly to the caller's handset with sub-second turn-taking latency.
Set up your first SIP-integrated voice agent
Connecting your existing telephony infrastructure to AI agents does not have to be complicated. You can build, configure, and test a fully conversational voice agent using your own SIP trunk in just a few minutes.
To begin, create a developer account to claim your free 50 minutes of call time. From there, you can configure your first agent, connect your Twilio or Exotel trunk, and run automated QA calls immediately. If you need help with high-volume enterprise routing or custom SIP headers, you can also talk to our integration engineering team for hands-on onboarding support.
Frequently Asked Questions
Can I use both Indian and international SIP trunks on the same Bolti agent?
Yes. You can assign multiple phone numbers from different SIP trunks (such as an Exotel trunk for India and a Twilio trunk for international calls) to a single Bolti agent. The agent will handle concurrent incoming calls from all assigned trunks.
Does Bolti charge extra for bringing my own SIP trunk (BYOC)?
No. Bolti does not charge extra platform fees for using your own SIP trunks. You only pay Bolti's standard platform rate (starting at ₹6/minute pay-as-you-go) for the AI voice processing, while your telephony carrier bills you directly for the SIP trunk minutes.
What audio codecs does Bolti support for SIP trunking?
Bolti supports standard telephony codecs including G.711 μ-law (PCMU) and A-law (PCMA), as well as high-definition Opus codecs for platforms that support wideband audio routing.
How does Bolti handle SIP call transfers?
You can configure your Bolti agent with tools that trigger a SIP REFER or call transfer command. This allows the AI agent to gracefully transfer a live call back to your human support team or call center queue on Exotel or Twilio.