When an extension pattern selection device is activated, a normal mode is displayed on a screen of a monitor. An operator presses a manual mode switch key of an operation unit to switch the display mode of the screen from the normal mode to an extension pattern manual rearrangement mode. In the extension pattern manual rearrangement mode, the operator rearranges extension patterns so that frequently selected extension patterns P may be displayed at upper positions. Thus, the frequently selected extension patterns P are more preferentially displayed than the other extension patterns P.