telnyx-voice-advanced-curl

name	telnyx-voice-advanced-curl
description	Advanced call control features including DTMF sending, SIPREC recording, noise suppression, client state, and supervisor controls. This skill provides REST API (curl) examples.
metadata	{"author":"telnyx","product":"voice-advanced","language":"curl","generated_by":"telnyx-openapi-pipeline"}

Telnyx Voice Advanced - curl

Installation

# curl is pre-installed on macOS, Linux, and Windows 10+

Setup

export TELNYX_API_KEY="YOUR_API_KEY_HERE"

All examples below use $TELNYX_API_KEY for authentication.

Error Handling

All API calls can fail with network errors, rate limits (429), validation errors (422), or authentication errors (401). Always handle errors in production code:

# Check HTTP status code in response
response=$(curl -s -w "\n%{http_code}" \
  -X POST "https://api.telnyx.com/v2/messages" \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"to": "[phone]", "from": "[phone]", "text": "Hello"}')

http_code=$(echo "$response" | tail -1)
body=$(echo "$response" | sed '$d')

case $http_code in
  2*) echo "Success: $body" ;;
  422) echo "Validation error — check required fields and formats" ;;
  429) echo "Rate limited — retry after delay"; sleep 1 ;;
  401) echo "Authentication failed — check TELNYX_API_KEY" ;;
  *)   echo "Error $http_code: $body" ;;
esac

Common error codes: 401 invalid API key, 403 insufficient permissions, 404 resource not found, 422 validation error (check field formats), 429 rate limited (retry with exponential backoff).

Join AI Assistant Conversation

Add a participant to an existing AI assistant conversation. Use this command to bring an additional call leg into a running AI conversation.

POST /calls/{call_control_id}/actions/ai_assistant_join — Required: conversation_id, participant

Optional: client_state (string), command_id (string)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "conversation_id": "v3:abc123",
  "participant": {}
}' \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/ai_assistant_join"

Returns: conversation_id (uuid), result (string)

Update client state

Updates client state

PUT /calls/{call_control_id}/actions/client_state_update — Required: client_state

curl \
  -X PUT \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "client_state": "aGF2ZSBhIG5pY2UgZGF5ID1d"
}' \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/client_state_update"

Returns: result (string)

Start Conversation Relay

Start a Conversation Relay session on an active call. Conversation Relay connects the call audio to your WebSocket so your application can exchange realtime messages with the caller while Telnyx handles speech recognition and text-to-speech. Only one AI Assistant or Conversation Relay session can be active on a call at a time.

POST /calls/{call_control_id}/actions/conversation_relay_start

Optional: assistant (object), client_state (string), command_id (string), conversation_relay_dtmf_detection (boolean), conversation_relay_settings (object), conversation_relay_url (string), custom_parameters (object), dtmf_detection (boolean), greeting (string), interruptible (enum: none, any, speech, dtmf), interruptible_greeting (enum: none, any, speech, dtmf), interruption_settings (object), language (string), languages (array[object]), provider (string), structured_provider (object), transcription (object), transcription_engine (enum: Google, Telnyx, Deepgram, Azure, xAI, AssemblyAI, Speechmatics, Soniox, A, B), transcription_engine_config (object), tts_provider (string), url (string), voice (string), voice_settings (object)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/conversation_relay_start"

Returns: conversation_relay_id (string), result (string)

Stop Conversation Relay

Stop the active Conversation Relay session on a call.

POST /calls/{call_control_id}/actions/conversation_relay_stop

Optional: client_state (string), command_id (string)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/conversation_relay_stop"

Returns: result (string)

Send DTMF

Sends DTMF tones from this leg. DTMF tones will be heard by the other end of the call. Expected Webhooks:

There are no webhooks associated with this command.

POST /calls/{call_control_id}/actions/send_dtmf — Required: digits

Optional: client_state (string), command_id (string), duration_millis (int32)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "digits": "1www2WABCDw9"
}' \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/send_dtmf"

Returns: result (string)

SIPREC start

Start siprec session to configured in SIPREC connector SRS.

Expected Webhooks:

• siprec.started
• siprec.stopped
• siprec.failed

POST /calls/{call_control_id}/actions/siprec_start

Optional: client_state (string), connector_name (string), include_metadata_custom_headers (boolean), secure (boolean), session_timeout_secs (integer), sip_transport (enum: udp, tcp, tls), siprec_track (enum: inbound_track, outbound_track, both_tracks)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/siprec_start"

Returns: result (string)

SIPREC stop

Stop SIPREC session. Expected Webhooks:

• siprec.stopped

POST /calls/{call_control_id}/actions/siprec_stop

Optional: client_state (string), command_id (string)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/siprec_stop"

Returns: result (string)

Noise Suppression Start (BETA)

POST /calls/{call_control_id}/actions/suppression_start

Optional: client_state (string), command_id (string), direction (enum: inbound, outbound, both), noise_suppression_engine (enum: Denoiser, DeepFilterNet, Krisp, AiCoustics, aic_l_quail, aic_l_rook, aic_s_quail, aic_s_rook, quail_voice_focus_s, quail_voice_focus_xs), noise_suppression_engine_config (object)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/suppression_start"

Returns: result (string)

Noise Suppression Stop (BETA)

POST /calls/{call_control_id}/actions/suppression_stop

Optional: client_state (string), command_id (string)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/suppression_stop"

Returns: result (string)

Switch supervisor role

Switch the supervisor role for a bridged call. This allows switching between different supervisor modes during an active call

POST /calls/{call_control_id}/actions/switch_supervisor_role — Required: role

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "role": "barge"
}' \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/switch_supervisor_role"

Returns: result (string)

---

Webhooks

Webhook Verification

Telnyx signs webhooks with Ed25519. Each request includes telnyx-signature-ed25519 and telnyx-timestamp headers. Always verify signatures in production:

# Telnyx signs webhooks with Ed25519 (asymmetric — NOT HMAC/Standard Webhooks).
# Headers sent with each webhook:
#   telnyx-signature-ed25519: base64-encoded Ed25519 signature
#   telnyx-timestamp: Unix timestamp (reject if >5 minutes old for replay protection)
#
# Get your public key from: Telnyx Portal > Account Settings > Keys & Credentials
# Use the Telnyx SDK in your language for verification (client.webhooks.unwrap).
# Your endpoint MUST return 2xx within 2 seconds or Telnyx will retry (up to 3 attempts).
# Configure a failover URL in Telnyx Portal for additional reliability.

The following webhook events are sent to your configured webhook URL. All webhooks include telnyx-timestamp and telnyx-signature-ed25519 headers for Ed25519 signature verification. Use client.webhooks.unwrap() to verify.

Event	Description
callConversationEnded	Call Conversation Ended
callConversationInsightsGenerated	Call Conversation Insights Generated
callDtmfReceived	Call Dtmf Received
callMachineDetectionEnded	Call Machine Detection Ended
callMachineGreetingEnded	Call Machine Greeting Ended
callMachinePremiumDetectionEnded	Call Machine Premium Detection Ended
callMachinePremiumGreetingEnded	Call Machine Premium Greeting Ended
callReferCompleted	Call Refer Completed
callReferFailed	Call Refer Failed
callReferStarted	Call Refer Started
callSiprecFailed	Call Siprec Failed
callSiprecStarted	Call Siprec Started
callSiprecStopped	Call Siprec Stopped

Webhook payload fields

callConversationEnded

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.conversation.ended	The type of event being delivered.
data.id	uuid	Unique identifier for the event.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.created_at	date-time	Timestamp when the event was created in the system.
data.payload.assistant_id	string	Unique identifier of the assistant involved in the call.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call leg.
data.payload.call_session_id	string	ID that is unique to the call session (group of related call legs).
data.payload.client_state	string	Base64-encoded state received from a command.
data.payload.calling_party_type	enum: pstn, sip	The type of calling party connection.
data.payload.conversation_id	string	ID unique to the conversation or insight group generated for the call.
data.payload.duration_sec	integer	Duration of the conversation in seconds.
data.payload.reason	string | null	Reason the conversation ended.
data.payload.from	string	The caller's number or identifier.
data.payload.to

callConversationInsightsGenerated

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.conversation_insights.generated	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.calling_party_type	enum: pstn, sip	The type of calling party connection.
data.payload.insight_group_id	string	ID that is unique to the insight group being generated for the call.
data.payload.results	array[object]	Array of insight results being generated for the call.

callDtmfReceived

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.dtmf.received	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Identifies the type of resource.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.digit	string	The received DTMF digit or symbol.

callMachineDetectionEnded

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.machine.detection.ended	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.result	enum: human, machine, not_sure	Answering machine detection result.

callMachineGreetingEnded

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.machine.greeting.ended	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.result	enum: beep_detected, ended, not_sure	Answering machine greeting ended result.

callMachinePremiumDetectionEnded

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.machine.premium.detection.ended	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.result	enum: human_residence, human_business, machine, silence, fax_detected, not_sure	Premium Answering Machine Detection result.

callMachinePremiumGreetingEnded

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.machine.premium.greeting.ended	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.result	enum: beep_detected, no_beep_detected	Premium Answering Machine Greeting Ended result.

callReferCompleted

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.refer.completed	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Unique ID for controlling the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.sip_notify_response	integer	SIP NOTIFY event status for tracking the REFER attempt.
data.payload.to	string	Destination number or SIP URI of the call.

callReferFailed

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.refer.failed	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Unique ID for controlling the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.sip_notify_response	integer	SIP NOTIFY event status for tracking the REFER attempt.
data.payload.to	string	Destination number or SIP URI of the call.

callReferStarted

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.refer.started	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Unique ID for controlling the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.sip_notify_response	integer	SIP NOTIFY event status for tracking the REFER attempt.
data.payload.to	string	Destination number or SIP URI of the call.

callSiprecFailed

Field	Type	Description
data.record_type	enum: event	Identifies the resource.
data.event_type	enum: siprec.failed	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.failure_cause	string	Q850 reason why siprec session failed.

callSiprecStarted

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: siprec.started	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.

callSiprecStopped

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: siprec.stopped	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.hangup_cause	string	Q850 reason why the SIPREC session was stopped.