# Define external alarms in Amazon IoT SiteWise
<a name="define-external-alarms"></a>

External alarms contain the state of an alarm that you detect outside of Amazon IoT SiteWise.

## Define an external alarm (console)
<a name="define-external-alarm-console"></a>

You can use the Amazon IoT SiteWise console to define an external alarm on an existing asset model. To define an external alarm on a new asset model, create the asset model, and then complete these steps. For more information, see [Create asset models in Amazon IoT SiteWise](create-asset-models.md).

**To define an alarm on an asset model**

1. <a name="sitewise-open-console"></a>Navigate to the [Amazon IoT SiteWise console](https://console.amazonaws.cn/iotsitewise/).

1. <a name="sitewise-choose-models"></a>In the navigation pane, choose **Models**.

1. Choose the asset model for which to define an alarm.

1. Choose the **Alarm definitions** tab.

1. Choose **Add alarm**.

1. In **Alarm type options**, choose **External alarm**.

1. Enter a name for your alarm.

1. (Optional) Enter a description for your alarm.

1. Choose **Add alarm**.

## Define an external alarm (CLI)
<a name="define-external-alarm-cli"></a>

You can use the Amazon CLI to define an external alarm on a new or existing asset model.

To add an external alarm to an asset model, you add an alarm composite model to the asset model. An external alarm composite model specifies the `EXTERNAL` type and doesn't specify an alarm source property. The following example composite alarm defines an external temperature alarm.

```
{
  {{...}}
  "assetModelCompositeModels": [
    {
      "name": "BoilerTemperatureHighAlarm",
      "type": "AWS/ALARM",
      "properties": [
        {
          "name": "AWS/ALARM_TYPE",
          "dataType": "STRING",
          "type": {
            "attribute": {
              "defaultValue": "EXTERNAL"
            }
          }
        },
        {
          "name": "AWS/ALARM_STATE",
          "dataType": "STRUCT",
          "dataTypeSpec": "AWS/ALARM_STATE",
          "type": {
            "measurement": {}
          }
        }
      ]
    }
  ]
}
```

For more information about how to add a composite model to a new or existing asset model, see the following:
+ [Create an asset model (Amazon CLI)](create-asset-models.md#create-asset-model-cli)
+ [Update an asset model, component model, or interface (Amazon CLI)](update-asset-models.md#update-asset-model-cli)

After you define the external alarm, you can ingest alarm state to assets based on the asset model. For more information, see [Ingest an external alarm state in Amazon IoT SiteWise](ingest-external-alarm-state.md).