It is a transmission line for transmitting RF signals to a destination in a wired manner. 

Especially in a vehicle, it can efficiently transmit various electrical signals (Radio, TDMB, GPS, SDARS, HSDPA etc.) and transmits signals of Radio + TDMB + DAB for the purpose of use in domestic AVN system. 

In order to minimize the loss rate depending on the frequency, 1.5CS is mostly used.