Deflection of the electron beam in a cathode-ray tube. It is controlled either by means of two pairs of magnetic coils mounted around the tube (electromagnetic beam deflection) or by two pairs of plates mounted inside the tube (electrostatic beam deflection). Electromagnetic deflection is nonlinear with respect to the applied current, causing pincushion distortion of the image; this has to be compensated for by circuitry. Electrostatic deflection tends to be more expensive than electromagnetic deflection but is more accurate.