A special relay to mute audio when reversing to allow parking tones to be heard clearly. This relay is designed for aftermarket radio fittings where a parking sensor retention interface has been fitted.This relay will use a positive reverse gear signal to mute the new head unit: so when the car is reversing the radio is silent and the parking tone interface can be heard clearly.This relay kit comes with fitting instructions.To be used on vehicles where a parking sensor retention interface is needed when installing an aftermarket radio.Example Vehicles: Volvo XC90 BMW 3 Series E90 BMW 1 Series E80 Mini 2007> Citroen 2007> Peugeot 2007> Landrover Freelander 2 *This interface is activated by a positive reverse signal: most installations using CAN-Bus steering control interfaces will provide this signal: for some vehicles where a suitable interface is not present an alternative reverse gear signal will need to be used.