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# refer

> Send a SIP REFER to transfer a call at the SIP level via REST.

[transfer]: /docs/server-sdks/reference/typescript/rest/calling/transfer

Send a SIP REFER on an active call. This initiates a SIP-level transfer,
asking the remote endpoint to connect to a new destination. Unlike
[`transfer()`][transfer], which is
handled by SignalWire, a SIP REFER delegates the transfer to the remote
SIP endpoint.

> **Note**
>
> SIP REFER is only applicable to SIP calls. It will not work on PSTN calls.

## **Request**

### Schema (`calling.refer`)

```yaml
components:
  schemas:
    uuid:
      type: string
      format: uuid
      description: Universal Unique Identifier.
      title: uuid
    CallingReferDeviceType:
      type: string
      enum:
        - sip
      description: The device type. Currently only 'sip' is supported.
      title: CallingReferDeviceType
    Calling.ReferSipParams:
      type: object
      properties:
        to:
          type: string
          description: SIP URI to refer the call to (must start with `sip:`).
        from:
          type: string
          description: Optional SIP From URI (must start with `sip:` when provided).
        username:
          type: string
          description: Optional SIP authentication username.
        password:
          type: string
          description: Optional SIP authentication password.
      required:
        - to
      description: SIP REFER device parameters.
      title: Calling.ReferSipParams
    Calling.ReferDevice:
      type: object
      properties:
        type:
          $ref: '#/components/schemas/CallingReferDeviceType'
          description: The device type. Currently only 'sip' is supported.
        params:
          $ref: '#/components/schemas/Calling.ReferSipParams'
          description: SIP REFER parameters.
      required:
        - type
        - params
      description: Device configuration for SIP REFER.
      title: Calling.ReferDevice
    CallingCallRequestDiscriminatorMappingCallingReferParams:
      type: object
      properties:
        device:
          $ref: '#/components/schemas/Calling.ReferDevice'
          description: The SIP device to refer the call to.
        status_url:
          type: string
          format: uri
          description: HTTP or HTTPS URL that receives refer lifecycle webhooks.
      required:
        - device
      description: An object of parameters that will be utilized by the active command.
      title: CallingCallRequestDiscriminatorMappingCallingReferParams
    Calling.CallReferRequest:
      type: object
      properties:
        id:
          $ref: '#/components/schemas/uuid'
          description: The unique identifying ID of an existing call.
        params:
          $ref: >-
            #/components/schemas/CallingCallRequestDiscriminatorMappingCallingReferParams
          description: An object of parameters that will be utilized by the active command.
      required:
        - id
        - params
      title: Calling.CallReferRequest
```

## **Response**

### Schema (`Calling.CallResponse`)

```yaml
components:
  schemas:
    uuid:
      type: string
      format: uuid
      description: Universal Unique Identifier.
      title: uuid
    Calling.CallDirection:
      type: string
      enum:
        - inbound
        - outbound
        - outbound-api
      description: The direction of the call.
      title: Calling.CallDirection
    CallingCallLegSource:
      type: string
      enum:
        - realtime_api
      description: Source of this call.
      title: CallingCallLegSource
    Calling.ChargeDetails:
      type: object
      properties:
        description:
          type: string
          description: Description for this charge.
        charge:
          type: number
          format: double
          description: Charged amount.
      required:
        - description
        - charge
      description: One itemized charge applied to the call.
      title: Calling.ChargeDetails
    Calling.CallResponseStatus:
      type: string
      enum:
        - queued
        - initiated
        - created
        - ringing
        - answered
        - ending
        - ended
        - failed
        - canceled
        - completed
      description: The status of the call throughout its lifecycle.
      title: Calling.CallResponseStatus
    CallingCallLegType0:
      type: string
      enum:
        - relay_pstn_call
      title: CallingCallLegType0
    CallingCallLegType1:
      type: string
      enum:
        - relay_sip_call
      title: CallingCallLegType1
    CallingCallLegType2:
      type: string
      enum:
        - relay_webrtc_call
      title: CallingCallLegType2
    CallingCallLegType:
      oneOf:
        - $ref: '#/components/schemas/CallingCallLegType0'
        - $ref: '#/components/schemas/CallingCallLegType1'
        - $ref: '#/components/schemas/CallingCallLegType2'
      description: Type of this call.
      title: CallingCallLegType
    Calling.CallLeg:
      type: object
      properties:
        id:
          $ref: '#/components/schemas/uuid'
          description: >-
            The unique identifier of the call on SignalWire. This can be used to
            update the call programmatically.
        from:
          type: string
          description: The origin number or address.
        to:
          type: string
          description: The destination number or address.
        direction:
          $ref: '#/components/schemas/Calling.CallDirection'
          description: The direction of the call.
        source:
          $ref: '#/components/schemas/CallingCallLegSource'
          description: Source of this call.
        url:
          type:
            - string
            - 'null'
          description: The URL associated with this call.
        charge:
          type: number
          format: double
          description: Total charge for this call.
        created_at:
          type: string
          format: date-time
          description: The date and time when the call was created.
        charge_details:
          type: array
          items:
            $ref: '#/components/schemas/Calling.ChargeDetails'
          description: Details on charges associated with this call.
        status:
          oneOf:
            - $ref: '#/components/schemas/Calling.CallResponseStatus'
            - type: 'null'
          description: The status of the call.
        duration:
          type:
            - integer
            - 'null'
          description: The duration of the call in seconds.
        duration_ms:
          type:
            - integer
            - 'null'
          description: The duration of the call in milliseconds.
        billing_ms:
          type:
            - integer
            - 'null'
          description: The billable duration of the call in milliseconds.
        type:
          $ref: '#/components/schemas/CallingCallLegType'
          description: Type of this call.
        parent_id:
          oneOf:
            - $ref: '#/components/schemas/uuid'
            - type: 'null'
          description: The parent call ID if this is a child call.
      required:
        - id
        - from
        - to
        - direction
        - source
        - url
        - charge
        - created_at
        - charge_details
        - status
        - duration
        - duration_ms
        - billing_ms
        - type
        - parent_id
      description: Returned when the call is a standard PSTN, SIP, or WebRTC call.
      title: Calling.CallLeg
    CallingFabricDeviceLegSource:
      type: string
      enum:
        - realtime_api
      description: Source of this call.
      title: CallingFabricDeviceLegSource
    CallingFabricDeviceLegType:
      type: string
      enum:
        - fabric_subscriber_device_leg
      description: Type of this call.
      title: CallingFabricDeviceLegType
    Calling.FabricDeviceLeg:
      type: object
      properties:
        id:
          $ref: '#/components/schemas/uuid'
          description: >-
            The unique identifier of the call on SignalWire. This can be used to
            update the call programmatically.
        from:
          type: string
          description: The origin number or address.
        to:
          type: string
          description: The destination number or address.
        direction:
          $ref: '#/components/schemas/Calling.CallDirection'
          description: The direction of the call.
        source:
          $ref: '#/components/schemas/CallingFabricDeviceLegSource'
          description: Source of this call.
        url:
          type:
            - string
            - 'null'
          description: The URL associated with this call.
        charge:
          type: number
          format: double
          description: Total charge for this call.
        created_at:
          type: string
          format: date-time
          description: The date and time when the call was created.
        charge_details:
          type: array
          items:
            $ref: '#/components/schemas/Calling.ChargeDetails'
          description: Details on charges associated with this call.
        status:
          description: >-
            The status of the call. Always null for Fabric subscriber device
            legs.
        type:
          $ref: '#/components/schemas/CallingFabricDeviceLegType'
          description: Type of this call.
      required:
        - id
        - from
        - to
        - direction
        - source
        - url
        - charge
        - created_at
        - charge_details
        - status
        - type
      description: >-
        Returned when the call is a Fabric subscriber device leg. The `status`
        field is always null for this type.
      title: Calling.FabricDeviceLeg
    Calling.CallResponse:
      oneOf:
        - $ref: '#/components/schemas/Calling.CallLeg'
        - $ref: '#/components/schemas/Calling.FabricDeviceLeg'
      title: Calling.CallResponse
```

## **Example**

```typescript {9}
import { RestClient } from "@signalwire/sdk";

const client = new RestClient({
  project: "your-project-id",
  token: "your-api-token",
  host: "your-space.signalwire.com"
});

await client.calling.refer("call-id-xxx", {
  type: "sip",
  params: { to: "sip:sales@example.com" },
});
```

> Send a SIP REFER to transfer a call at the SIP level via REST.