If your vehicle has this feature, it allows the driver to return to the last used source: radio, cassette, or CD using the remote keyless entry transmitter. This feature can also store and recall AM and FM presets, volume, tone, and the last selected radio station. The number on the back of each transmitter, 1 or 2, corresponds to driver 1 or 2. If transmitter 1 is used to enter the vehicle, the last used audio source and/or settings set by driver 1 will be recalled. If transmitter 2 is used to enter the vehicle, the last used audio source and/or settings set by driver 2 will be recalled.