The Front Panel Lock function is intended to minimize the probability of unintentional adjustments to the system. The buttons and knobs on the front of the Control Unit (CU) will not function until unlocked, except for the power switch, which will power the unit off, and the Volume knob and Talk button, which will allow communication with a connected local headset. When the CU is first powered ON, it is always unlocked. Lock and unlock the CU front panel by pressing and holding the Home and Enter buttons simultaneously for five seconds.