Sending Commands for Programmable Voice

A Voice API command is sent with a call_control_id. The call_control_id allows a user to communicate to Telnyx the call_leg the user wants to control. It also helps Telnyx route the call to the location where the call is being managed, resulting in the lowest possible latency for Call Control interactions.

Like all other Telnyx API V2 requests, you must authenticate your Voice API command requests by sending the Authorization header with a value of an API Key. You can read more about API Keys here.

Credential Type	HTTP Header Format
API Key	Authorization: Bearer YOUR_API_KEY

To answer the call, send a POST request to the /actions/answer endpoint as shown in the example below.

Note

Don't forget to update YOUR_API_KEY here.

curl -X POST \
  --header "Content-Type: application/json" \
  --header "Accept: application/json" \
  --header "Authorization: Bearer YOUR_API_KEY" \
  https://api.telnyx.com/v2/calls/428c31b6-7af4-4bcb-b7f5-5013ef9657c1/actions/answer

Note

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Telnyx offers a broad range of commands to enable granular control of your call flows. Below are a list of those commands, and the webhooks the Telnyx Voice API platform will always send in response. When multiple webhooks are listed, you can expect to often, though not always, receive webhooks in the order provided.

Command	Expected Webhooks
Answer call	call.answered
Bridge call	call.bridged for Leg A call.bridged for Leg B
Dial	call.initiated call.answered or call.hangup call.machine.detection.ended - if answering_machine_detection was requested call.machine.greeting.ended - if answering_machine_detection was requested to detect the end of machine greeting
Forking start	call.fork.startedcall.fork.stopped
Forking stop	call.fork.stopped
Gather using audio	call.playback.started call.playback.ended call.dtmf.received - you may receive many of these webhooks call.gather.ended
Gather using speak	call.dtmf.received - you may receive many of these webhooks call.gather.ended
Hangup	call.hangup call.recording.saved - if the call is being recorded
Play audio url	call.playback.startedcall.playback.ended
Playback stop command	call.playback.ended or call.speak.ended
Recording start	no webhooks
Recording stop	call.recording.saved
Reject call	call.hangup
Send DTMF	no webhooks
Speak text	call.speak.startedcall.speak.ended
Transfer call	call.initiated call.bridged to Leg B call.answered or call.hangup

When you send a Voice API Command, you will immediately receive an http response. Responses include, but are not limited to:

HTTP Status Code	Message	Description
200	OK	The request succeeded.
403	Forbidden	The request was valid, however the user is not authorized to perform this action.
404	Not Found	The requested resource could not be found.
422	Invalid Parameters	The request has invalid parameters or the call is no longer active.