To adjust Brightness/Contrast please follow below (Mitel 5330e)

- specific button descriptions below - useful in the event the screen is unreadable

Hit the grey Settings button
Select Settings (4th button from bottom)
Select Br/con (4th from bottom)
Brightness+ (4th from top)
Br- (5th from top)
Contrast+ (6th from top)
Cont- (7th from top)
Select Save (top button)
Select Close (3rd from top)