See also:

Control Setting Suggestions for Various Weather Conditions
...

To Resume Speed
To resume a previously set speed, push the RES (+) button and release. Resume can be used at any speed above 20 mph (32 km/h). ...

Operating Instructions - Radio Mode
NOTE: The ignition switch must be in the ON or ACC position to operate the radio. Power Switch/Volume Control (Rotary) Push the ON/VOLUME control knob to turn on the radio. Press the ON/VOLUME con ...