Interfaces are radio wire harnesses that include a module for retaining steering wheel controls (SWC) such as volume up/down and skip. These controls are lost when the factory radio is replaced with a new aftermarket radio. In most cases, the wire harness plugs directly into the vehicle's factory connector that is behind the radio, providing the new aftermarket radio with power and sound. The interface harness is plugged into the SWC compatible aftermarket radio for SWC retention.
Interfaces are also offered for vehicles equipped with a fiber optic amplified sound system. These options will include an additional module for the fiber optic signal and in some cases may retain a factory information display that is lost with installing an aftermarket radio.