---
title: externalSyncDevice
framework: avfoundation
role: symbol
role_heading: Instance Property
path: avfoundation/avcapturedeviceinput/externalsyncdevice
---

# externalSyncDevice

The external sync device currently being followed by this input.

## Declaration

```swift
var externalSyncDevice: AVExternalSyncDevice? { get }
```

## Discussion

Discussion This readonly property returns the AVExternalSyncDevice instance you provided in follow(_:videoFrameDuration:delegate:). This property returns nil when an external sync device is disconnected or fails to calibrate.

## See Also

### Synchronizing with external devices

- [isExternalSyncSupported](avfoundation/avcapturedeviceinput/isexternalsyncsupported.md)
- [follow(_:videoFrameDuration:delegate:)](avfoundation/avcapturedeviceinput/follow(_:videoframeduration:delegate:).md)
- [unfollowExternalSyncDevice()](avfoundation/avcapturedeviceinput/unfollowexternalsyncdevice().md)
- [activeExternalSyncVideoFrameDuration](avfoundation/avcapturedeviceinput/activeexternalsyncvideoframeduration.md)