---
title: kAudioSession_AudioRouteChangeKey_PreviousRouteDescription
framework: audiotoolbox
role: symbol
role_heading: Global Variable
path: audiotoolbox/kaudiosession_audioroutechangekey_previousroutedescription
---

# kAudioSession_AudioRouteChangeKey_PreviousRouteDescription

Describes the previous audio route.

## Declaration

```swift
let kAudioSession_AudioRouteChangeKey_PreviousRouteDescription: CFString!
```

## Discussion

Discussion A CFDictionary object that describes the previous audio route. For specifics on the contents of this dictionary, see kAudioSession_AudioRouteKey_Inputs and kAudioSession_AudioRouteKey_Outputs.

## See Also

### Constants

- [kAudioSessionInputRoute_BluetoothHFP](audiotoolbox/kaudiosessioninputroute_bluetoothhfp.md)
- [kAudioSessionInputRoute_BuiltInMic](audiotoolbox/kaudiosessioninputroute_builtinmic.md)
- [kAudioSessionInputRoute_HeadsetMic](audiotoolbox/kaudiosessioninputroute_headsetmic.md)
- [kAudioSessionInputRoute_LineIn](audiotoolbox/kaudiosessioninputroute_linein.md)
- [kAudioSessionInputRoute_USBAudio](audiotoolbox/kaudiosessioninputroute_usbaudio.md)
- [kAudioSessionOutputRoute_AirPlay](audiotoolbox/kaudiosessionoutputroute_airplay.md)
- [kAudioSessionOutputRoute_BluetoothA2DP](audiotoolbox/kaudiosessionoutputroute_bluetootha2dp.md)
- [kAudioSessionOutputRoute_BluetoothHFP](audiotoolbox/kaudiosessionoutputroute_bluetoothhfp.md)
- [kAudioSessionOutputRoute_BuiltInReceiver](audiotoolbox/kaudiosessionoutputroute_builtinreceiver.md)
- [kAudioSessionOutputRoute_BuiltInSpeaker](audiotoolbox/kaudiosessionoutputroute_builtinspeaker.md)
- [kAudioSessionOutputRoute_HDMI](audiotoolbox/kaudiosessionoutputroute_hdmi.md)
- [kAudioSessionOutputRoute_Headphones](audiotoolbox/kaudiosessionoutputroute_headphones.md)
- [kAudioSessionOutputRoute_LineOut](audiotoolbox/kaudiosessionoutputroute_lineout.md)
- [kAudioSessionOutputRoute_USBAudio](audiotoolbox/kaudiosessionoutputroute_usbaudio.md)
- [kAudioSession_AudioRouteChangeKey_CurrentRouteDescription](audiotoolbox/kaudiosession_audioroutechangekey_currentroutedescription.md)