---
title: "Send Real-Time Text (T.140) on a SIP leg"
method: POST
path: "/legs/{id}/rtt"
tags: ["Legs"]
---

# Send Real-Time Text (T.140) on a SIP leg

`POST /legs/{id}/rtt`

Sends UTF-8 text on the leg's RTT (T.140 / RFC 4103) media stream. Requires that the SDP offer/answer agreed on an m=text section with the remote UA. Enable RTT on the server with RTT_ENABLED=true.

## Request body

- RTTRequest
  - `text` string, required — UTF-8 text to send. May be one or more characters and may include T.140 control codes (e.g. backspace U+0008, CR/LF).

## Response `200`

Text sent

- StatusResponse
  - `instance_id` string — Instance identifier
  - `status` string, required

## Other responses

- `400` — Invalid JSON or empty text
- `404` — Leg not found
- `409` — RTT was not negotiated for this leg
- `500` — Send failed

## Changes

- **2026-05-11** `7ab34b92424f` — 1 info
  - endpoint added
- **2026-03-26** `d09c97c6ca8c` — 1 breaking
  - api path removed without deprecation

[Change history](https://skmtc.dev/voiceblender/apis/voiceblender-api/changes/legs/:id/rtt/post.md)

---

[API](https://skmtc.dev/voiceblender/apis/voiceblender-api.md) · [All operations](https://skmtc.dev/voiceblender/apis/voiceblender-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/voiceblender/voiceblender-api/revisions/7c997a2166e4/schema)