Installation location: Behind the car audio screen host, or car power amplifier. Function: Convert external RCA audio signal to optical fiber signal, and mit to the car amplifier through optical fiber. The sound came from the sound of the car.For example: For Mercedes-Benz E Class Carton audio, when you need toreplace the car screen host, in order to retain the car amplifier, you canc. If there is no sound after installing the fiber optic box,Pls check it as following steps: 1. Confirm whether the power supply is connected well, measure with a multimeter, yellow --- battery power 12V, black --- ground wire, no need to connect ACC power supply. 2. Confirm whether the gateway signal is connected well, CAN-H, CAN-L. 3. In the optical fiber communication of the vehicle, all the optical fiber signals must be ableto communicate normally. Due to the damage of certain electrical equipment of the vehicle, the optical fiber communication is abnormal. At this time, it is necessary to short-circuit theoptical fiber signal of the damaged device, (common For example: 6-disc CD, telephonecommunication module, or directly install the optical fiber audio box to the caramplifier). Name:Optical Fiber Audio Decoding Box Working voltage:12V Fitment: For Mercedes Benz vehicles For 2000-2003 S/CL class Mercedes Benz For 2000-2002 E Class Mercedes Benz For 2003-2004 SL Mercedes Benz For 2001-2004 C/CLK Mercedes Benz For 2000-2005 ML Mercedes Benz Colour:Blue Material:plastic Package Contents: 1 x Fiber-Optic(MOST) Decoder Box 1 x Connection Cable Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.