There is an electron gun at the other end of the tube. It consists of a cathode and a control grid. The cathode is a metal piece which emits electrons into the vacuum tube when the cathode is indirectly heated by the heating coil. The grid is a negatively charge metal mesh placed on front of a cathode. It controls the brightness of the image on the screen by controlling the amount of electrons allowed to pass through the vacuum tube.
Some cathode ray tubes also have a focusing anode and an accelerating anode. Both anodes are connected to a positive potential that it mush higher than the cathode potential. The focusing anode concentrates the electrons beam into a tight and narrow beam. The accelerating anode then accelerates this beam to high speeds so that the electrons can hit the fluorescent screen, which then emits visible light.