> ## Documentation Index > Fetch the complete documentation index at: https://docs.open.cx/llms.txt > Use this file to discover all available pages before exploring further. > Return a caller that a Classical IVR transferred to your SIP endpoint, so the flow can route them to a team. Use when your system is done with the call. # Hand back a transferred call When a Classical IVR transfers a caller to a SIP destination, the caller stays on the OpenCX call while your SIP endpoint talks to them. Call this endpoint, instead of hanging up, when the caller should continue with the organization. OpenCX hangs up your SIP leg, then the IVR continues with the steps after the transfer, usually a transfer to a team. The caller keeps the same call, recording and session throughout. Send the session ID you received in the `X-OPENCX-SESSION-ID` SIP header of the transfer. The destination must list `X-OPENCX-SESSION-ID` among its allowed headers if it uses an allowlist. * Create the API key with the **Hand back transferred calls** (`phone-calls:write`) scope. That scope cannot read or change any other phone configuration. A `phone:write` key can also hand calls back. * Pass an optional `summary` of the conversation so far. It replaces the session's summary before the teammate is connected, so they see it when the call rings. It is saved only when the hand-back is accepted. * Repeating a successful hand-back returns the same response and changes nothing; a `summary` sent with the repeat is ignored. * A `409` means the session has no transferred call waiting: your leg has not answered yet, your leg or the caller already hung up, or the session has no SIP transfer. Hanging up without calling this endpoint returns the caller to the IVR, which continues with the `completed` outcome. * A `404` means the session does not exist in the organization that owns the API key. Do not hang up your leg first: OpenCX hangs it up for you once the hand-back is accepted. If your leg hangs up before the hand-back arrives, the hand-back is still accepted for a few seconds. ## OpenAPI ````yaml post /phone/calls/hand-back openapi: 3.1.0 info: title: OpenCX API description: > OpenCX is an AI-powered, all-in-one platform for customer support and outbound communications. Use this API to manage your OpenCX organization's AI agents, actions, conversations, contacts, and more. To get started, generate a new API key from the dashboard. ## Authentication All API endpoints require authentication using a Bearer token. You can generate an API key from your OpenCX dashboard. ## Rate Limiting API requests are rate limited to ensure fair usage. The current limits are: - 100 requests per minute for standard endpoints - 1000 requests per minute for streaming endpoints ## Error Handling The API uses standard HTTP status codes and returns detailed error messages in the response body. version: 1.0-beta license: name: MIT url: https://opensource.org/licenses/MIT servers: - url: http://localhost:8080 description: Development - url: https://api.open.cx description: Production security: - bearerAuth: [] paths: /phone/calls/hand-back: post: summary: Hand back a transferred call description: >- Returns a caller that a Classical IVR transferred to your SIP endpoint. Your SIP leg is hung up, and the IVR continues with the steps after the transfer (usually routing the caller to a team) on the same call, recording and session. Call it instead of hanging up when the caller should continue with the organization. Repeating a successful hand-back returns the same response and ignores its summary. Returns 409 when the session has no transferred call waiting: before your leg answered, or after your leg or the caller hung up. operationId: handBackPhoneCall requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/HandBackCallInput' responses: '201': description: Default Response content: application/json: schema: $ref: '#/components/schemas/HandBackCallOutput' '500': description: Internal Server Error content: application/json: schema: $ref: '#/components/schemas/ErrorDto' components: schemas: HandBackCallInput: $schema: https://json-schema.org/draft/2020-12/schema $id: '#/components/schemas/HandBackCallInputInput' type: object properties: session_id: type: string format: uuid pattern: >- ^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|ffffffff-ffff-ffff-ffff-ffffffffffff)$ description: >- The session of the call to hand back, as received in the X-OPENCX-SESSION-ID SIP header summary: description: >- Your summary of the conversation so far. Saved as the session's summary before a teammate is connected. type: string minLength: 1 maxLength: 10000 required: - session_id additionalProperties: false HandBackCallOutput: $schema: https://json-schema.org/draft/2020-12/schema $id: '#/components/schemas/HandBackCallOutput' type: object properties: session_id: type: string format: uuid pattern: >- ^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|ffffffff-ffff-ffff-ffff-ffffffffffff)$ status: type: string const: handed_back required: - session_id - status additionalProperties: false ErrorDto: type: object properties: statusCode: type: integer message: type: string error: type: string securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.