Television manufacturers started adding a child lock on their televisions to prevent children from watching inappropriate programming. Dell televisions have a child lock that, when enabled, locks all of the buttons on the control panel except the "Power" button. Children can turn on the television, but they cannot switch between channels. In order to return the buttons to normal working order, unlock your Dell television.
Press and hold the "VOL +" and "CH +" buttons on the television's control panel for approximately 10 seconds to disable the child lock.
Turn on the television and use the television's control panel buttons to change the channel or raise the volume. If the control panel buttons do not work, repeat Step 1.
Lock the television again by pressing the "Menu" button and selecting "Setup." Choose "OSD Settings" from the menu and then "TV Button Lock." All of the buttons on the television, except for the "Power" button, are now inoperable.