Ultravox

Ultravox is a realtime voice model platform with low time-to-first-byte and configurable agents. The bridge proxies Teler call audio into your Ultravox agent and relays its response back over the same WebSocket.

Reference repos

Python teler-ultravox-bridge

Node teler-ultravox-node-bridge

Prerequisites

• An Ultravox account with an agent created
• The agent_id of that Ultravox agent
• A Teler account with an active API key
• One Teler phone number on your account
• An ngrok auth token (for local development)
• Docker and Docker Compose

Configuration

Variable	Required	Default	Description
ULTRAVOX_API_KEY	yes	none	Your Ultravox API key.
ULTRAVOX_AGENT_ID	yes	none	The Ultravox agent ID to connect calls to.
TELER_API_KEY	yes	none	Your Teler API key.
NGROK_AUTHTOKEN	yes (local)	none	ngrok auth token.

5-minute setup

Python

git clone https://github.com/frejun-tech/teler-ultravox-bridge
cd teler-ultravox-bridge
cp .env.example .env
docker compose up -d --build

Node

git clone https://github.com/frejun-tech/teler-ultravox-node-bridge
cd teler-ultravox-node-bridge
cp .env.example .env
docker compose up -d --build

Initiate a call

curl -X POST http://localhost:8000/api/v1/calls/initiate-call \
  -H "Content-Type: application/json" \
  -d '{
    "from_number": "+91XXXXXXXXXX",
    "to_number":   "+91XXXXXXXXXX"
  }'

Architecture

Standard 3-endpoint shape (see Bridge). The bridge holds two WebSockets (Teler ↔ bridge ↔ Ultravox) and pumps audio between them.

Troubleshooting

Symptom	Likely cause	Fix
Agent not responding	Wrong ULTRAVOX_AGENT_ID	Verify in Ultravox dashboard
401 from Ultravox	Invalid ULTRAVOX_API_KEY	Rotate the key
Phone rings then drops	Bridge unreachable from public internet	Check ngrok status

Next steps

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