The iDN55 has two audio output channels; a docking connector on top of the unit and a USB port in the front of the unit. The iHome + Sleep app will send the wake signal to the channel which was “last” used to play music. If you last played music via the dock connector, the wake signal will be sent to the device connected to the dock. If you last played music via the USB port, the wake signal will be sent to the device connected to the USB.