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    "iOS: 18.0.0 -",
    "iPadOS: 18.0.0 -",
    "macCatalyst: 18.0.0 -",
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  "title" : "HMCharacteristicTypeActiveIdentifier"
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# HMCharacteristicTypeActiveIdentifier

An index that maps to the current active Input Source service.

```
let HMCharacteristicTypeActiveIdentifier: String
```

## Discussion

This characteristic describes the current input source of a television by referencing the [`HMServiceTypeInputSource`](/documentation/HomeKit/HMServiceTypeInputSource). The Active Identifier characteristic’s value should be a valid value within the identifiers of the Input Source service instances linked to the television service. The value of the characteristic is a `UInt32` integer.

---

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