Convert external audio signal to optical fiber signal, and transmit to the car amplifier through optical fiber. The sound came from the sound of the car. Application scenarios: For example: for W211 Carton audio, when you need toreplace the car screen host, in order to retain the car amplifier, you canchoose to install optical fiber Audio box. Note that for audio is not suitable Wiring method: yellow-B+ battery positive, black-GND ground, red right audio input, white left audio input Installation location: Behind the car audio screen host, or car power amplifier. Product name:Optical Fiber Audio Decoding Box Working voltage:12V Fitment: for E series W211 2005 2006 2007 2008 for S series W220 2004 2005 2006 for SL series W129 2005 2006 2007 2008 for series W219 2005 2006 2007 2008 for series W215 2004 2005 2006 for series W171 2005 2006 2007 2008 without SD card slot NOTE: All above series cannot install speakers Special attention: when you connect the cable, If the sound is abnormal. Please note that thisphenomenon is not a problem with our fiber conversion module. This is the vehicle's fibercommunication system cannot communicate normally. 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 Colour:Black Material:plastic Package Contents: 1 * Decoder Box 1set * fiber short-circuit rings 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.