d - Digital radio
Digital radio - Digital radio offers perfect crackle- and hiss-free reception, as it does not rely on the strength of the signal, whereas an analogue system does.
Digital radio signals are converted into 'binary digits' or 'bits', which are compressed and then transmitted. The DAB processor in your car is able to identify this information and reproduce it without distortion or interference. This also means you don't have to retune the radio as you travel.
As with digital television, compression of the signals allows more channels to be broadcast within the same bandwidth.
Ford was the first manufacturer to offer a digital radio as a dealer-fit option, although systems are available for virtually every car from electrical and hi-fi outlets.