Disc players can "read codes" and "decode", but in order to reduce costs, their decoding functions are generally relatively primitive. To increase the level of "decoding" and make the sound more beautiful, it is necessary to be equipped with an independent decoder and a power amplifier with decoding function. Optical fiber cables are needed between the disc drive and the decoder, and between the disc drive and the decoding power amplifier. It is connected with a coaxial cable and is responsible for transmitting the digital audio signal "read" from the discplayer to an independent decoder or a power amplifier with decoding function to "decode" it into an audio signal. This transmission method is often used in high-end audio systems.