Skip to main content
The <Transcription> verb enables real-time speech-to-text transcription for the call.

​
Attributes

ATTRIBUTEDESCRIPTIONOPTIONSDEFAULT
language Language to use for speech recognition. See languages in transcription_engine_config. en
interimResults Whether to send also interim results. If set to false, only final results will be sent. Applies to transcriptionEngine A only. false
transcriptionEngine Engine to use for speech recognition. Available engines: Google (default), Telnyx, Deepgram, Azure, xAI, AssemblyAI, Soniox, Speechmatics. Each engine supports different models and languages - see model attribute and examples below. Legacy values “A” (maps to Google) and “B” (maps to Telnyx) are supported for backward compatibility. Google, Telnyx, Deepgram, Azure, xAI, AssemblyAI, Soniox, Speechmatics, A, BGoogle
transcriptionTracks Indicates which leg of the call will be transcribed. Use inbound for the leg that requested the transcription, outbound for the other leg, and both for both legs of the call. inbound, outbound, bothinbound
transcriptionCallback URL that tells Telnyx where to make its GET or POST requests with transcription data. -
transcriptionCallbackMethod HTTP request type used for transcriptionCallback. GET, POSTPOST
model Optional model to use with the specified transcription engine. Format is vendor/model-name — e.g. deepgram/nova-2, deepgram/nova-3, azure/fast, assemblyai/universal-streaming, soniox/stt-rt-v4, speechmatics/standard, xai/grok-stt. The vendor must match transcriptionEngine. If not specified, the engine’s default model will be used. On Deepgram, defaults to deepgram/nova-3. See transcription models in transcription_engine_config. -
hints Hints to improve transcription accuracy. On Deepgram, this maps to the Nova-2 keyword biasing feature and is supported only on model="deepgram/nova-2"; it is silently dropped on Nova-3 (use keyterms instead). Accepts a comma-separated string. -
keyterms Deepgram Nova-3 keyterm prompting. Biases recognition toward domain-specific terms or brand names. Supported only on model="deepgram/nova-3"; silently dropped on Nova-2 (use hints instead). Accepts a comma-separated string. -
smartFormat Disable Deepgram’s smart formatting so the transcript stays lowercase with no punctuation. Deepgram-only; silently dropped on other engines. true
apiKeyRef Reference to the API key for authentication. See integration secrets documentation for details. The parameter is optional as defaults are available for some regions. -
region Region to use with the specified transcription engine. Required for Azure. See regions in transcription_engine_config. -

​
Examples

Example 1: Basic transcription using Google (default) 
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Start>
    <Transcription language="en" interimResults="true" transcriptionCallback="/transcription" />
  </Start>
</Response>
Example 2: Google with phone call optimized model 
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Start>
    <Transcription
      transcriptionEngine="Google"
      model="phone_call"
      language="en-US"
      interimResults="true"
      transcriptionCallback="/transcription" />
  </Start>
</Response>
Example 3: Telnyx engine with Whisper model 
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Start>
    <Transcription
      transcriptionEngine="Telnyx"
      model="openai/whisper-large-v3-turbo"
      language="es"
      transcriptionCallback="/transcription" />
  </Start>
</Response>
Example 4: Deepgram with Nova-3 model 
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Start>
    <Transcription
      transcriptionEngine="Deepgram"
      model="deepgram/nova-3"
      language="fr"
      transcriptionCallback="/transcription" />
  </Start>
</Response>
Example 5: Azure with Fast model and credentials 
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Start>
    <Transcription
      transcriptionEngine="Azure"
      model="azure/fast"
      language="en-US"
      apiKeyRef="your-azure-api-key-ref"
      region="eastus"
      transcriptionCallback="/transcription" />
  </Start>
</Response>
Example 6: Azure with Realtime model 
<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Start>
    <Transcription
      transcriptionEngine="Azure"
      model="azure/realtime"
      language="en-US"
      region="westus"
      transcriptionCallback="/transcription" />
  </Start>
</Response>

​
Expected callbacks

If transcriptionCallback is set, transcription results are sent as they become available. See Transcription Callback for the full payload reference.