Question

How can I send or inject DTMF digits into an active call while using bidirectional Media Streams (<Connect><Stream>) without interrupting the existing WebSocket connection?

Product

Programmable Voice, Media Streams

Answer

The raw Media Streams WebSocket protocol does not currently support outbound DTMF injection. Using <Play digits="..."/> is the only way to emit RFC-2833 DTMF, but it requires interrupting and reconnecting the stream.

Consider these alternatives to avoid interrupting the active call:

1. Twilio Conversation Relay: If building an AI voice agent, Conversation Relay natively supports sending mid-call DTMF directly over the WebSocket via a sendDigits message without dropping the stream.
2. Pre-Dialing (SendDigits): If the IVR path is known in advance, pass the SendDigits parameter (e.g., SendDigits="wwww1234#") when creating the outbound call via the REST API to play the tones automatically upon answer.

Additional Information

• TwiML <Connect><Stream> Documentation
• Twilio Conversation Relay Documentation
• Programmable Voice REST API: Making Calls (SendDigits parameter)