abstract:Beam deflection tubes, were cathode ray tubes with an electron gun, a beam intensity control grid, a screen grid, sometimes a suppressor grid, and two electrostatic deflection electrodes on opposite sides of the electron beam, that could direct the rectangular beam to either of two anodes in the same plane. They were used as two-quadrant, single-balanced mixers or (de-)modulators with very linear qualities, their mode of operation similar to one-half of today's Gilbert Cells, by applying one, unbalanced, signal f1 to the control grid, and the other, balanced, signal f2 to the deflection electrodes, then extracting the balanced mixing products f1-f2 and f1+f2 from the two anodes.