glow tube: a gas-discharge tube consisting of a cold cathode and a diode in a tube filled with gas; the color of the glow depends on the particular gas
gas-discharge tube: a tube in which an electric discharge takes place through a gas
cartesian coordinate: one of the coordinates in a system of coordinates that locates a point on a plane or in space by its distance from two lines or three planes respectively; the two lines or the intersections of the three planes are the coordinate axes