What does the button with the Bluetooth icon mean on the 512?

The Bluetooth icon button controls the speaker’s pair mode and also acts as an indicator. When the button is flashing, the speaker is currently in pair mode and open to connect to a device. If the button is solid, it means a device is currently connected to the speaker. In order to disconnect a device from the speaker, you can press and hold the button until you hear the notification that the speaker is in pair mode.