[. . . ] It is thus recommended to disconnect the GND wire of the negative battery pole before you start with any installation work. [. . . ] When mounting the ZE-NC520 always pay proper attention not to damage any of the wires, plugs or other parts such as the external TMC module. Avoid applying too much mechanical force especially when pushing the unit back into the slot. If you want to use the external microphone, remove the purple connector with the wire bridge, activate the external microphone in the Bluetooth setup menu and plug in the purple connector of the external microphone. If you want to switch back using the internal microphone later on, the purple plug with the wire bridge must be inserted again ­ after the connector of the external microphone has been unplugged. The TMC box has been removed in the following pictures to deliver a better overview. Finally plug the antenna connector of the car into the antenna adapter of the TMC module. Removal of the radio trim cover: Remove the screws holding the radio trim cover and the AC control panel. Carefully pry off the cover and unplug the power supply of the board clock. [. . . ] Carefully pry off the cover and unplug the power supply of the board clock. [. . . ]