This is a audio car kit, It is a replacement of CD changer. It can be easily installed and used. The installation and usage are the same as CD changer’s installation and usage, Simply plug in USB disc/ SD card, You can play audio through you car audio system and enjoy music in you car. | Easy to installing ,no damage to original car decoration. Different module firmware version for different types of protocol of car stereos. | Connected with wire harness, not FM signal controlled, Hi-Fi guanranteed. | Controlled by vehicle Head Unit , support steering wheel operation. | Supports external audio source(MP4,PSP, Mobile phone)via AUX in port