Interface Leads Interface Leads Product description Installation description Line-In cable 68656 for Ford US models -2003 Line-In cable 68656 for Ford US models -2003 Interface Leads are used for car stereos with a Line-In function or VDA preparation. It enables the use of the car speakers when answering/making calls from your cell phone by using the radios built-in mute function. Speaker-function: This is achieved by connecting the carkit directly to the cars Line-In input/VDA connector.