The instruction by Air Traffic Control to "squawk ident" is an instruction for the pilot to press the "ident" button on his/her transponder which will illuminate the aircraft on the controllers screen. Instructing an aircraft to "squawk ident" is another way for Air Traffic Control to positively identify the aircraft in question. Additionally, in the event of a "lost comms" situation where an aircraft loses radio contact, ATC may request the aircraft to "squawk ident" which would signal that although the aircraft can't reply on the radio, they are receiving the transmission from Air Traffic Control.