More and more digital interconnects are used to lead the signal loss freely from one device to another. Especially if the source is digital and corrections are still taking place, such as room correction, or a separate DAC, it is nice if the signal can be passed without intermediate conversions. The most commonly used in the audio systems is the S/PDIF coaxial connection with RCA plugs or BNCplugs. The impedance of the cable is 75 OHM: the main feature to transmit the digital signal interference-free. Because this cable transmits a stereo signal, you only need one per source. Of course also suitable for multi-channel applications (surround sound).