Manual mode is selected/deselected by pressing and releasing the Scroll and the Mode keys at the same time. 'Power' is displayed in the lower display when the 4400 is in manual mode.
If you do not need access to the Auto/Manual modes:
1) Make sure that you are in the automatic mode (Lower display is not 'Power').
Enter Setup mode:
2) Press the SCROLL and the the UP ARROW keys (at the same time) and release.
3) Enter your Unlock code with the UP or Down Arrow keys. (Unlock code as shipped by ISE is 10)
4) Press the Scroll key to enter setup mode.
5) Press SCROLL until lower display shows: A/M Enab. Using UP or DOWN Arrows change parameter value to OFF. This will prevent the control from being switched between Auto and Manual modes.