Build & Deploy AI Voice Agents rapidly with Voicegain Telephony Bot API. Connect a LLM Chatbot to telephony & speech resources. Replace your legacy Touchtone or Speech-Enabled IVR.
Control the entire pipeline — telephony, STT, and AI — with no third-party dependencies.
Use our proprietary ASR or train custom models for domain-specific accuracy.
Skip external platforms. Voicegain runs on its own SIP infrastructure for full control.
Integrate any large language model (OpenAI, Cohere, local LLMs) for flexible deployments.
Generative AI is disrupting customer service. Large language models can understand and conduct human conversations at scale. Voicegain can help you deploy Generative AI powered voice assistant that can replace traditional tree-based IVRs and act as an AI Coach to your frontline call center staff.
Today’s callers expect smart, natural conversations — not robotic menus or endless button-pressing. Legacy IVRs frustrate users, increase drop-offs, and slow down support. It’s time for a smarter solution.
Voicegain powers fast, flexible phone automation across tasks, funnels, and support flows — trusted in healthcare, retail, finance, and more.
Share delivery updates, ETA changes, and alert customers to status changes or delays.
Verify orders for products, services, or food delivery — and send real-time updates.
Collect caller details, qualify interest, and pass leads directly to your CRM or sales team.
Resolve common questions instantly using synced content from your support or help desk tools.
Trigger payment reminders, provide account status, and escalate unpaid cases when needed.
Schedule, confirm, or reschedule bookings, all in a single phone interaction.
Build exactly what you need, where you need it — with nothing hidden, nothing locked in.
Create your bot using your preferred LLM framework — Langchain, Flowise, OpenAI, or custom logic.
Start a SIP or PSTN call. Voicegain handles the signaling, media, and live audio stream.
Process speech with STT, generate replies using your AI, and respond using TTS — instantly.
Voicegain works with your existing contact center, CPaaS, and AI tools. If it supports SIP INVITE or SIP REFER, it integrates.
Tested with leading platforms — compatible with any system that initiates a SIP INVITE.
Works with any CPaaS provider that supports SIP INVITE or SIP REFER.
Fully compatible with LLMs and conversational AI frameworks — no vendor lock-in.
We protect your voice data — and give you full control over your logic and compliance layer.
Built on experience. Trusted in production. Made for developers.
We’ve been building and refining voice infrastructure since before LLMs were a thing.
Our platform is made for engineers — not sales decks, not lock-ins, not hand-holding.
Powering production systems in healthcare, telecom, enterprise, and much more.
Transparent, usage-based billing. Only pay for what you stream, transcribe, and speak.
Use any AI engine — OpenAI, Claude, Langchain, etc. You only pay for Voicegain usage; LLM tokens are billed separately by your provider.
Update Dec 2020: We have renamed RTC Callback APIs to Telephony Bot APIs to better reflect how developers can use these APIs - which is build Voice Bots, IVRs.
If you have wanted to voice enable your Chatbot or build your own Telephony based Voice Bot or a Speech-enabled IVR, Voicegain has built an API that is really cool - Release 1.12.0 of Voicegain Speech-to-Text Platform now includes Telephony Bot APIs (formerly called RTC Callback APIs in the past).
Voicegain Telephony Bot APIs enables any NLU/Bot Framework to easily integrate with PSTN/telephony infrastructure using either (a) SIP INVITE of Voicegain platform from a CPaaS platform of your choice or (b) purchasing a phone number directly from Voicegain portal and pointing it to your Bot. You can then use these callback style APIs to (i) play prompts (ii) recognize speech utterances or DTMF digits (iii) allow for barge-in and several other exciting features. We offer sample code that will help you easily integrate a Bot Framework of your choice to our Telephony Bot APIs.
If you do not have a Bot Framework, thats okay too. You can write the logic in any backend programming language (Python, Java or Node.JS) that can serialize responses in a JSON format and interact with our Callback style APIs. Voicegain also offers a declarative YAML format to define the call flow and you can host this YAML file logic and interact with these APIs. Developers can also code and deploy the application logic in a server-less computing environment like Amazon Lambda.
Many enterprises - in banking, financial services , health care, telecom and retail - are stuck with legacy telephony based IVRs that are approaching obsolescence.
Voicegain's Telephony Bot APIs provide a great future-proof upgrade path for such enterprises. Since these APIs are based on web callbacks, they can interact with any backend programming language. So any backend web developer can design, build and maintain such apps.
With Telephony Bot APIs, integration becomes much simpler for developers.
1) You can SIP INVITE the Voicegain Speech-to-Text/ASR platform to a SIP/RTP session for as long as is needed. We support SIP integration with CPaaS platforms like Twilio, Signalwire and Telnyx. We also support CCaaS platforms like Genesys, Cisco and Avaya.
2) We also support direct phone number ordering and SIP Trunks from the Voicegain Web Console. More integrations will be added soon.
Telephony Bot APIs are based on web callbacks where the actual program/ implementation is on the Client side and the Voicegain Telephony Bot APIs define the Requests and Responses. The meaning of Requests and Responses is reversed w.r.t what you would see in a normal Web API:
Below is an example of a simple phone call interaction which is controlled by Telephony Bot API. The sequence diagram shows 4 callbacks during a toy survey call:
Telephony Bot API supports 4 types of actions:
Each call can be recorded (two channel recording) and then transcribed. The recording and the transcript can be accessed from the portal as well as via the API.
Features coming soon:
One of the previous blog posts described a Voice Bot built using Twilio, Voicegain, RASA, and AWS Lambda. Twilio was used for telephony (phone numbers, SIP Trunking, TwiML for call control) Voicegain provided the ASR/speech recognition, while AWS Lambda was coordinating the actions. The setup works but is involved. The need to pass the speech recognition results via S3 (as Lambda is stateless and does not have memory between function calls) may occasionally cause delays in requests and responses.
Voicegain now integrates with Amazon Chime Voice Connector to offer a pay as you go SIP Trunking service directly from the Voicegain web console. You can also purchase phone numbers and receive inbound calls. Support for making outbound Speech IVR calls is in the works.
Of course, we continue to support developer that use Twilio and SignalWire using simple SIP INVITE - this blog describes how.
The sequence diagram is provided below. It is very simple. Basically, the sequence of operations is as follows:
The sample code for the Lambda function (in python and node.js versions) is available on our github.
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