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Voice API Features

Powerful Voice API features

Build smarter voice applications with full access to advanced call logic and network-level control.

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The most-loved Voice API features

  • Bi-directional streaming from client to server and server to client
    Real-time media streaming

    Stream bi-directional RTP audio over secure WebSockets for real-time speech access. Ideal for voice-AI assistants and real-time coaching platforms that analyze speech on the fly.

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  • Text-to-speech

    Play dynamic, natural-sounding voices in 40 + languages and accents. Select normal, neural, or HD output from Telnyx, Polly, Azure, or ElevenLabs to power lifelike prompts and responses.

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  • Telnyx API sample code
    Speech-to-text

    Convert voice to text in real-time with low-latency, high accuracy engines from Telnyx or Google and automatic speaker separation for clear multi-party transcripts.

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  • Conversational AI commands

    Add voice bots to any call in minutes by chaining TTS, STT, and LLM logic via simple AIGather and AIAssistant commands, with no extra middleware or SIP scripting needed.

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  • Employee answers call at contact center
    Call recording

    Start or stop single- or dual-channel recordings at any moment for compliance, training, or playback, with secure storage.

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  • Click to Call Image- Women typing on laptop
    Browser/App Calling

    Add carrier-grade voice to any web or mobile app. Telnyx WebRTC handles signaling, NAT traversal, and encrypted media so users can place and receive calls right in the browser, no plugins or softphones required.

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Powerful call control features

  • Call escalation-call operators image
    Essential call control

    Take full control of every leg of a call with one-line API commands. Route callers, move them between endpoints, or cleanly end sessions in real time.

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  • Employee answers call at contact center
    Call recording

    Start or stop single- or dual-channel recordings at any moment for compliance, training, or playback, with secure storage.

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  • Custom call flows Image- man reading on cellphone
    SIP Refer handoffs

    Pass an active call to another SIP endpoint without dropping audio, enabling warm transfers and carrier-grade failover.

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  • Man takes phone call on park bench
    Audio playback

    Inject MP3 or WAV prompts (think announcements, ads, or hold music) directly into a live call.

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  • Woman sends text message
    DTMF collection

    Gather keypad input to drive IVRs, menu navigation, or PIN entry, with flexible timeouts and validation rules.

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  • Woman on conference call
    Conference calling

    Bridge multiple participants worldwide into a single, high-quality audio stream, complete with mute, record, and participant management via API.

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  • Number masking

    Protect caller privacy by replacing real numbers with temporary, anonymized proxies—all handled transparently by the Telnyx platform.

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  • Noise suppression

    Remove background hiss, hum, and chatter so voices stay front-and-center, even from busy call-center floors or noisy cafés.

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  • Private network illustration
    HD Voice

    Use 16 kHz wideband audio on eligible networks for richer, more natural-sounding conversations.

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  • Woman working on computer
    Insights and analytics

    Track and optimize every call in real time. Get real-time call status and sentiment scores to your stack so you can monitor, troubleshoot, and optimize every conversation in real time.

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  • Man makes call and gets routed through IVR
    Real-time webhooks and events

    Receive instant JSON callbacks for call status, media fork handshakes, and transcription results so your app stays perfectly in sync.

  • Product Thumbnail SIP Trunking-Communications
    SIPREC

    Using a legacy system but want to take advantage of AI? No problem, we also support SIPREC. Client and server support for standards-based call recording that streams dual-channel RTP.

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CUSTOMER STORIES
Telnyx media forking gives Replicant low-latency access to audio packets to be able to feed our AI models. In many cases, Telnyx was the fastest provider that was there on the market.
Customer Quote Replicant

Benjamin Gleitzman

CTO, Replicant

Read customer story
Voice API for developers

Start building

Get the developer docs, tools and support to build.

curl -X POST \
  --header "Content-Type: application/json" \
  --header "Accept: application/json" \
  --header "Authorization: Bearer YOUR_API_KEY" \
  --data '{"connection_id": "uuid", "to": "+18005550199", "from": "+18005550100"}' \
  https://api.telnyx.com/v2/calls
  • Icon Resources Docs

    Developer-first documentation

    Explore quickstart guides, tutorials, code samples, and a full API reference to help you launch and scale with confidence.

    Explore docs
  • Icon Resources Article

    What is a Voice API?

    Get a clear breakdown of how programmable voice works, what it costs, and the features to look for when building voice into your app.

    Read article
  • Icon Resources ebook

    Real-time speech-to-text

    Explore how real-time transcription supports natural interactions, improves responsiveness, and helps power multilingual AI conversations.

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