Juniper Allegro CE Owner's Manual page 94

If you are not using a USB Power Dock to connect your Allegro with
your PC, tap on the Change button to access the change connection
screen.
Tapping on the down arrow accesses the drop-down list of available
connection options. Tap on the Com type your Allegro is using and
tap on OK to save the new setting. If you do not want to change the
COM port, tap on X to cancel out of the Change Connection screen
and return to the PC Connection Properties screen.
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