The term PART OF CRT is composed of two crossword solutions, RAY (3 letters) and TUBE (4 letters). A cathode RAY TUBE (CRT) is an electronic device that uses a vacuum TUBE to display images. It was the primary technology used in television sets and computer monitors for many years before being replaced by LCD and other flat-panel technologies. The RAY portion of the term refers to the electron beam that is used to create the image on the screen, while the TUBE portion refers to the vacuum TUBE that contains the electron beam.