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# open(using:)

Opens the engagement session.

```
final func open(using token: CustomerEngagement.Token? = nil) async throws
```

## Parameters

`token`

`The Customer Engagement token used to authenticate your credentials.
If you omit the token, you must have already created a valid [`PaymentCardReaderSession`](/documentation/ProximityReader/PaymentCardReaderSession) before calling this method.

## Discussion> Throws: ``doc://com.apple.ProximityReader/documentation/ProximityReader/CustomerEngagementSession/Error`` if the open request fails. This method can also throw ``Foundation/URLError``.

---

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