The lever on a lightning control console that simultaneously dims all the channels from one cut to the next

The lever on a lighting control console that simultaneously dims all the channels from one cut to the next is a crossfader.

A crossfader can be defined as a control on a DJ mixer that allows the mixes to be created, so nowadays is a very basic tool.

The crossfaders became common in the '70s when they were used by the DJ to make mixes.