If the factory-installed OEM radio in a vehicle controlled by CAN Bus needs to be replaced with an aftermarket radio, a specific CAN Bus adapter is required. Both specific and universal CAN Bus adapters convert relevant digital data from the vehicle-specific data bus into analog signals. Depending on the vehicle, various signals such as ignition power, lighting, reverse gear signal, or speed signal are read and provided in analog form for different retrofit solutions. Note: CAN Bus specifications can be found under the vehicle-specific wiring harness numbers.