A low voltage cathode ray oscillograph

A sensitive cathode ray oscillograph is described which operates at the low potential of from 300 to 400 volts. The electron stream comes from a thermionic cathode and is focused by the action of ionized gas in the tube. This gas, at a pressure of a few thousandths of a millimeter, serves to reduce to 1 mm. diameter a spot which would be 1 cm. across in a high vacuum tube. The sensitivity of the tube is such that the deflection of the spot is about 1 mm. per volt applied between deflector plates. When using magnetic deflection, a pair of coils 4 cm. in diameter, placed on the sides of the tube produces a deflection of approximately 1 mm. per ampere-turn of the coils. — Editor.