Skip to main content
DTMF (Dual-Tone Multi-Frequency) events are generated when a participant presses keys (0-9, *, #) on their phone or SIP device during a call. These events are useful for building IVR flows, collecting user input, or triggering actions in your application.
This page covers the SIP platform side: enabling DTMF on the gateway and the event payload. To handle DTMF from your agent code, see DTMF Handling.

​
Enabling DTMF Events

DTMF event detection can be enabled in two ways:
  • Via Dashboard:
    • When creating or editing a SIP gateway in the Zero Runtime dashboard, enable the DTMF option.
  • Via API:
    • Set the enableDtmf parameter to true when creating or updating a SIP gateway using the API.
Once enabled, DTMF events will be detected and published for all calls routed through that gateway.

​
Listening to DTMF Events

To listen DTMF events in a Zero Runtime room, you can subscribe to the DTMF_EVENT topic using the PubSub system. This allows your application to react to DTMF input in real time. Sample Event Payload:
Payload Fields:
  • message: Description of the event.
  • senderId: The unique ID of the participant who sent the DTMF input.
  • timestamp: When the event was received (ISO format).
  • topic: Always DTMF_EVENT for these events.
  • senderName: Name of the participant (if available).
  • id: Unique event/message ID.
  • payload.number: The DTMF digit pressed (0-9, *, #).
  • payload.timestamp: Timestamp (in ms) when the digit was pressed.

​
Use Cases

  • Build IVR menus and collect user input during calls.
  • Trigger actions in your app based on keypresses (e.g., press 1 for support, 2 for sales).
  • Log or analyze DTMF input for compliance or analytics.
DTMF events are available for both inbound and outbound SIP calls, as long as the gateway is configured with DTMF enabled.