A picture to be televised is projected on to at photo sensitive cathode, and the resulting electron stream is focused on to the plane of an anode, where it is swept to and fro, past a central aperture, by an applied scanning voltage. The electrons that pass through the aperture strike against a series of target electrodes, which form an electron multiplier housed in the same tube as the camera.
According to the invention the whole device is rendered inoperative, during the idle or flyback stroke of the scanning operation, by applying an intermittent negative pulse to one of the target electrodes of the electron multiplier. Preferably two pulses of opposite sign are applied simultaneously to two electrodes, so that the signal current is cut off during the flyback stroke without producing any unbalanced impulse in the output circuit.
Baird Television, Ltd., and V A Jones (addition to 470785). Application date March 23rd, 1937: No. 492602.
From Wireless World February 2, 1939.