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The config verb allows developers to change the default speech settings during a session or to collect speech or DTMF input in the background while other verbs run. This verb is non-blocking, so the specified settings are changed immediately and the application proceeds with the next verb. 
{
  "verb": "config",
  "synthesizer": {
    "vendor": "microsoft",
    "language": "de-DE",
    "voice": "de-DE-KillianNeural"
  },
  "recognizer": {
    "vendor": "google",
    "language": "de-DE"
  },
  "bargeIn": {
    "enable": true,
    "sticky": true,
    "input": ["speech", "digits"],
    "actionHook": "/userInput",
    "partialResultHook": "/partialInput",
    "finishOnKey": "#",
    "numDigits": 5,
    "minDigits": 1,
    "maxDigits": 5,
    "interDigitTimeout": 3000,
    "dtmfBargein": true,
    "minBargeinWordCount": 2
  },
  "fillerNoise": {
    "enable": true,
    "url": "https://example.com/filler.wav",
    "startDelaySecs": 2
  },
  "vad": {
    "enable": true,
    "voiceMs": 250,
    "silenceMs": 500,
    "strategy": "adaptive",
    "mode": 3
  },
  "speechFallback": {
    "type": "dial",
    "reason": "recognizerFailure",
    "dial": {
      "number": "+49123456789"
    },
    "refer": {
      "uri": "sip:user@example.com"
    }
  },
  "actionHookDelayAction": {
    "enabled": true,
    "noResponseTimeout": 5000,
    "noResponseGiveUpTimeout": 15000,
    "retries": 2,
    "actions": [
      {
        "verb": "say",
        "text": "Waiting for response..."
      }
    ],
    "giveUpActions": [
      {
        "verb": "say",
        "text": "No response received. Moving on."
      }
    ]
  },
  "boostAudioSignal": "+3dB",
  "listen": {
    "startTimeout": 5000,
    "stopTimeout": 2000
  },
  "notifyEvents": true,
  "onHoldMusic": "https://example.com/hold.mp3",
  "referHook": "/sipRefer",
  "reset": ["recognizer", "synthesizer"],
  "record": {
    "action": "startCallRecording",
    "siprecServerURL": "sip:recording@example.com",
    "recordingID": "call12345",
    "headers": {
      "X-Custom-Header": "value"
    }
  },
  "sipRequestWithinDialogHook": "/sipRequest",
  "amd": true
}

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Configuration

The following table lists the available parameters:
ParameterTypeDescriptionRequired
actionHookDelayAction.enabledbooleanEnables or disables the delayed action hook behavior. When enabled, the system waits for the configured action hook to respond before executing any delay or give-up actions.No
actionHookDelayAction.noResponseTimeoutnumberThe timeout in milliseconds to wait for a response from the action hook before executing the delay actions, such as prompting the user with a say verb.No
actionHookDelayAction.noResponseGiveUpTimeoutnumberThe timeout in milliseconds to wait before executing the give-up actions if the action hook never responds.No
actionHookDelayAction.retriesnumberThe number of retry attempts to call the action hook before giving up.No
actionHookDelayAction.actionsarrayAn array of verbs to execute while waiting for the action hook response, such as a say verb to provide feedback to the user.No
actionHookDelayAction.giveUpActionsarrayAn array of verbs to execute if the action hook never responds, for example, a say verb to inform the user and continue the application.No
amdbooleanEnables Answering Machine Detection (AMD) to distinguish whether the call is answered by a human or a machine.No
bargeIn.enablebooleanEnables background listening for speech or DTMF input while other verbs execute. If disabled, stops any background listening tasks currently running.No
bargeIn.stickybooleanIf both bargeIn.enable and bargeIn.sticky are true, another background gather automatically starts after detecting speech or DTMF input, allowing continuous input collection.No
bargeIn.actionHookstringA webhook URL to invoke when user input is collected by the background gather. The default is voice.No
bargeIn.partialResultHookstringA webhook URL to receive interim transcription results during background gathering. Useful for providing real-time feedback or logging partial input.No
bargeIn.inputarraySpecifies allowed input types: ['digits'], ['speech'], or ['digits', 'speech'].Yes
bargeIn.finishOnKeystringThe DTMF key that signals the end of input in the background gather.No
bargeIn.numDigitsnumberThe exact number of DTMF digits expected to gather.No
bargeIn.minDigitsnumberThe minimum number of DTMF digits expected to gather. The default is 1.No
bargeIn.maxDigitsnumberThe maximum number of DTMF digits expected to gather.No
bargeIn.interDigitTimeoutnumberThe time in milliseconds to wait between DTMF digits after reaching the minimum number of digits.No
bargeIn.dtmfBargeinbooleanEnables DTMF barge-in so that entering a DTMF tone can interrupt audio playback during background gathering.No
bargeIn.minBargeinWordCountnumberThe minimum number of words the user must speak before triggering barge-in. Helps prevent accidental interruptions during speech prompts.No
boostAudioSignalstring | numberSpecifies the number of decibels to increase or decrease the outgoing audio signal level (e.g., -6 dB or +3 dB). Default is 0 dB.No
fillerNoise.enablebooleanEnables or disables filler noise played while waiting for user input or during processing.Yes (if used)
fillerNoise.urlstringThe URL to the MP3 or WAV audio file to play as filler noise.No
fillerNoise.startDelaySecsnumberThe delay in seconds before starting filler noise playback.No
listenobjectA nested listen verb that streams session audio to a remote server via WebSocket.No
notifyEventsbooleanEnables event notifications over WebSocket connections. Verbs must include an id property to use this feature.No
onHoldMusicstringThe URL to an audio file to play when the session is placed on hold.No
recognizerobjectContains configuration options for the speech recognition engine. This includes language selection, hints, diarization, and other advanced settings.No
recognizer.vendorstringThe speech recognition provider to use, for example, Google, Amazon, or Azure. The vendor determines transcription quality, supported languages, and feature availability.Yes
recognizer.labelstringA custom label to identify this recognizer instance in logs or dashboards. Helpful when multiple recognizers are configured.No
recognizer.languagestringThe primary language code for transcription, for example, en-US for English, fr-FR for French. Determines how speech is interpreted.No
recognizer.hintsarrayAn array of words or phrases that may appear in the audio and should be recognized more accurately. Useful for domain-specific terms, names, or technical vocabulary.No
recognizer.hintsBoostnumberA numeric value specifying how strongly the recognizer should prioritize the hint words. Higher numbers give stronger emphasis, improving accuracy for key terms.No
recognizer.altLanguagesarrayAn array of additional language codes that the recognizer can use for multilingual audio. Allows recognition of mixed-language content.No
recognizer.profanityFilterbooleanIf true, the recognizer will automatically remove or mask profanity from the transcription output.No
recognizer.interimbooleanIf true, returns partial transcription results as the audio is being processed. Useful for live captions or real-time feedback.No
recognizer.punctuationbooleanIf true, punctuation marks, for example, periods or commas, are included in the transcription to improve readability.No
recognizer.diarizationbooleanIf true, enables speaker diarization, which assigns segments of the transcript to individual speakers.No
recognizer.diarizationMinSpeakersnumberThe minimum number of speakers expected in the audio. Helps the diarization algorithm distinguish between speakers accurately.No
recognizer.diarizationMaxSpeakersnumberThe maximum number of speakers expected in the audio. Prevents the algorithm from splitting speech unnecessarily.No
recognizer.vadobjectVoice Activity Detection settings. Determines how the system detects when someone is speaking vs. silence, improving transcription timing and accuracy.No
recognizer.fallbackVendorstringSpecifies an alternative transcription vendor to use if the primary vendor fails. Ensures reliability in critical workflows.No
recognizer.fallbackLanguagestringLanguage code to use for the fallback vendor. Must match a language supported by the fallback provider.No
referHookstringA webhook URL to invoke when a SIP REFER is received in the session.No
resetstring | arrayResets either the recognizer or synthesizer to default application settings.No
record.actionstringThe call recording action: startCallRecording, stopCallRecording, pauseCallRecording, or resumeCallRecording.Yes
record.siprecServerURLstring | arrayThe SIP URI(s) for the SIPREC server. Required if record.action is startCallRecording.Conditional
record.recordingIDstringA user-defined identifier for the recording.No
record.headersobjectSIP headers to include in the SIPREC request.No
sipRequestWithinDialogHookstringA webhook to invoke when a SIP request (e.g., INFO, NOTIFY, REFER) is received within a dialog.No
speechFallback.typestringThe type of fallback action (e.g., dial or refer).Yes (if used)
speechFallback.reasonstringThe reason for executing the fallback (e.g., recognizerFailure).No
speechFallback.dialobjectA dial verb to execute as fallback if speech recognition fails.No
speechFallback.referobjectA sip:refer verb to execute as fallback if speech recognition fails.No
synthesizerobjectSession-level text-to-speech settings. See Synthesizer Properties for details.No
synthesizer.vendorstringThe TTS provider to use, for example, google, aws, microsoft, deepgram, elevenlabs, nuance, or custom:<provider-name>. The vendor determines the available voices, languages, and engine options. See supported speech vendors.Yes
synthesizer.labelstringA custom label to identify this synthesizer instance. Useful when multiple TTS configurations from the same vendor are configured. Must match a label defined in the Voice Gateway Application.No
synthesizer.languagestringThe language code for the speech output, for example, en-US or de-DE. Required if a vendor is defined.No
synthesizer.voicestring | objectThe specific voice to use. Can be a string representing the vendor-specific voice name (for example, en-US-Wavenet-F for Google TTS) or an object with advanced properties. Defaults to the Application-level TTS voice if not provided.No
synthesizer.enginestringThe TTS engine type. Options are:
  • standard — the default engine
  • neural — a high-quality natural voice
  • generative — an experimental AI voice
  • long-form — optimized for long text
No
synthesizer.genderstringThe desired voice gender: MALE, FEMALE, or NEUTRAL. Used for vendors that support gender selection.No
synthesizer.optionsobjectA vendor-specific TTS options object. Common options include speakingRate (0.25–4.0), pitch (-20–20), and volumeGainDb (-96–16). These control the speech speed, pitch, and volume.No
synthesizer.fallbackVendorstringAn alternative TTS vendor to use if the primary vendor fails or returns an error.No
synthesizer.fallbackLabelstringA label for the fallback TTS instance. Must match a label defined in the Voice Gateway Application.No
synthesizer.fallbackLanguagestringThe language code for the fallback synthesizer. Defaults to the primary language if not provided.No
synthesizer.fallbackVoicestring | objectThe voice for the fallback synthesizer. Can be a string or object.No
transcribeobjectA nested transcribe verb for background transcription of audio.No
vad.enablebooleanEnables or disables Voice Activity Detection (VAD).Yes (if used)
vad.voiceMsnumberDuration in milliseconds of voice required to trigger detection.No
vad.silenceMsnumberDuration in milliseconds of silence required to end detection.No
vad.strategystringThe VAD detection strategy (e.g., adaptive or fixed).No
vad.modenumberNumeric value representing VAD sensitivity mode.No

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