How do I lock or unlock the front panel on a DS1000 series television demodulator?

The lock/unlock sequence is given on page 2-13 of the user manual (P/N 071090502).

Press the DISPLAY key until the text "FRONT PANEL LOCKED" or "FRONT PANEL UNLOCKED" appears on the LCD display. Then press the arrow keys in the following sequence: up, right, down, left, then enter to lock or unlock the front panel.