This is a plug and play adapter cable for Audi cars with ISO and Mini ISO connectors at the back of the original radio and with rear  amplified audio systems.
This cable has an adjustable  line-out converter built into the speaker cables, this drops the output levels from high level to low level in order to work with the amplifier in the car. This lead is suitable for cars with both the rear amplified audio systems. 

The CANbus ignition interface generates a key present ignition supply to the new stereo, this means the stereo will turn on with the first click of the key and stay on until the key is removed from the ignition barrel.

This cable has a built in Phantom powered antenna adapter. This adapts from the antenna connector in the car, known as an ISO antenna connector, to a standard aftermarket antenna connector, known as a DIN antenna connector, for the new stereo.

NOTE: Most early model Audi TT cars do not have an ignition signal on the CANbus data, this interface will not generate an ignition supply on these earlier models.