Compatible Fiber-Optic Interface:When installing this interface, you must make sure that the Fiber-Optic signal loop is not broken. If you have other devices which can include CD Changer, satellite radio, and telephone module, they must stay connected so the fiber optic signal loop is consistent. To identify if you have a Fiber-Optic audio system, you can check the vehicle in the following ways:Some vehicles will have clear markings on the speaker grills indicating the presence of an upgraded audio system. Connection Instruction: 1. Please take the black plug A out of our decoder box's Fiber-Optic interface C, then remove the grey plastic protective cover D; 2. Please find and remove your car's original Fiber-Optic plug B; 3. Connect your car's original Fiber-Optic plug B to the removed black plug A of our decoder box's Fiber-Optic interface(in step 1) ; 4. Then reinsert the removed black plug A to our decoder box's Fiber-Optic interface C; 5. Plug the "Power and AUX Audio Input Connection Cable" in the power socket of our decoder box, connect the cables on the other ends like this: Red ACC Cable: to ACC cable(usually it is the red cable from aftermarket head unit main harness); Yellow BATTERY B+ Cable: to Positive pole of car battery(usually it is the yellow cable from aftermarket head unit main harness); Black GND Cable: to GND cable(usually it is the black cable from aftermarket head unit main harness); AUX-RIN, AUX-LIN cable: to the Front Right and Front Left AUX audio output port of aftermarket head unit. Compatible Car Models: for Benz ML/GL/R Class (2005-2011) E/CLS/SLK Class (2009-2012) for Porsche 911 (2005-2012) boxster (2005-2012) Cayman (2004-2012) for BMW E9X (E90 E91 E92 E93) E7X (E70 E71) F0X (F01/F02/F03) Colour:As Shown Material:ABS