Electron tube mounted on terminal base for investigating the design and operation of modern cathode ray tubes. The electron beam can be deflected by an electric field produced by the deflection plates integrated into the tube, and by a magnetic field from three external coils mounted on a ring. A Wehnelt cylinder is used to focus the beam. A gas filling and fluorescent screen makes it possible to observe the beam in the tube. A continuously adjustable saw-tooth generator can be used to analyze and visualize time dependent processes. The device comes with a socket and printed wiring scheme.