### Main Features Accessible via API

Source: https://help.yeastar.com/en/p-series-appliance-edition/developer-guide/about-this-guide.html/index

Overview of the core functionalities that can be managed or monitored on the Yeastar P-Series PBX System through its APIs.

```APIDOC
## Main Features Accessible via API

### Description
Lists the primary capabilities provided by the Yeastar P-Series PBX System APIs, allowing third-party applications to perform various operations.

### Functionalities
- **Query PBX Parameters and Status**: Retrieve information about the PBX configuration and its current operational state.
- **Configure PBX Features**: Modify settings and enable/disable features on the PBX.
- **Control Calls**: Initiate, manage, and terminate calls programmatically.
- **Monitor Events**: Receive real-time notifications about significant occurrences within the PBX.
```

--------------------------------

### API Request and Response

Source: https://help.yeastar.com/en/p-series-appliance-edition/developer-guide/about-this-guide.html/index

Third-party applications can interact with the Yeastar P-Series PBX System by sending API requests to query features, configure parameters, and control calls. The PBX responds with the requested resources.

```APIDOC
## API Request and Response

### Description
Allows third-party applications to send requests to the PBX to query features, configure parameters, and control calls. The PBX returns a response with the requested resources.

### Method
GET, POST, PUT, DELETE (Specific methods depend on the API endpoint)

### Endpoint
(Specific endpoints depend on the API functionality)

### Parameters
(Details depend on the specific API request)

### Request Example
(Example request body will vary based on the API call)
```json
{
  "action": "query",
  "resource": "call_status"
}
```

### Response
#### Success Response (200)
- **status** (string) - Indicates the success of the request.
- **data** (object) - Contains the requested resources or results.

#### Response Example
```json
{
  "status": "success",
  "data": {
    "call_count": 5,
    "active_calls": [
      {
        "id": "12345",
        "caller": "1001",
        "callee": "1002",
        "duration": 60
      }
    ]
  }
}
```
```

--------------------------------

### Event Subscription and Notification

Source: https://help.yeastar.com/en/p-series-appliance-edition/developer-guide/about-this-guide.html/index

Third-party applications can subscribe to specific PBX events. The PBX will then proactively send notifications to the application in real-time when these events occur.

```APIDOC
## Event Subscription and Notification

### Description
Enables third-party applications to subscribe to desired PBX events. The PBX will proactively send notifications to the application about changes in real-time.

### Method
POST (for subscription)

### Endpoint
(Specific subscription endpoint will be provided)

### Parameters
#### Request Body
- **event_type** (string) - Required - The type of event to subscribe to (e.g., 'call_started', 'voicemail_received').
- **callback_url** (string) - Required - The URL where the PBX should send event notifications.

### Request Example
```json
{
  "event_type": "call_ended",
  "callback_url": "https://your-app.com/api/event-handler"
}
```

### Response
#### Success Response (200)
- **subscription_id** (string) - A unique identifier for the subscription.
- **status** (string) - Confirmation of the subscription.

#### Response Example
```json
{
  "subscription_id": "sub_abc123",
  "status": "subscribed"
}
```

### Event Notification Example (Sent to callback_url)
```json
{
  "event": "call_ended",
  "timestamp": "2023-10-27T10:30:00Z",
  "data": {
    "call_id": "12345",
    "caller": "1001",
    "callee": "1002",
    "duration": 120
  }
}
```
```

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