Daktronics DF-1020 - Manual (Page 55)

Gas Price 6-7
Display Operation
LED Test
Select menu item 6, LED Test, to test the LED digits on the display.
LCD Screen Action
LED TEST
ENTER TO TEST Press the < ENTER > key to cycle the display
digits between all LEDs on and all LEDs off.
ENTER TO TEST
CLEAR TO EXIT Press < ENTER > send the test command to the
sign.
Press < CLEAR > to exit the test mode