1. To cut off the electron beam of a television picture tube, camera tube, or cathode-ray oscilloscope tube during the process of retrace by applying a rectangular pulse voltage to the grid or cathode during each retrace interval. Also known as beam blank. 2. The result of the final cutting operation on a natural crystal.

Related Terms


In a radar set, a sharp voltage pulse which is applied to the modulator tubes to fire the transmitter, applied simultaneously to the sweep generator to start the electron beam moving radially from the sweep origin to the edge of the face of the cathode-ray tube.


The direct-current bias voltage that must be applied to the grid of an electron tube to stop the flow of anode current.


  1. The winding of a power transformer that furnishes alternating-current heater or filament voltage for one or more electron tubes. 2. A process for fabricating a composite structure in which continuous fiber reinforcement (glass, boron, silicon carbide), either previously impregnated with a matrix material or impregnated during winding, are wound under tension over a rotating core.


  1. The emission of electrons from one solid into another. 2. The process of injecting a beam of electrons with an electron gun into the vacuum chamber of a mass spectrometer, betatron, or other large electron accelerator.


  1. One of the electrodes of graphite used in a mercury cell to produce chlorine by electrolysis. 2. The rod of graphite which is inserted into the mercury-pool cathode of an ignitron to start current flow. 3. The collector of electrons in a beam power tube or other high-current tube.


The electron current flowing through an electron tube from the cathode to the anode. Also known as plate current.


Limiting the maximum output voltage of a vacuum tube circuit by driving the grid beyond cutoff.


  1. The slowly decaying luminescence of the screen of the cathode-ray tube after excitation by an electron beam has ceased. 2. A broad, high arch of radiance or glow seen occasionally in the western sky above the highest clouds in deepening twilight, caused by the scattering effect of very fine particles of dust suspended in the upper atmosphere.


  1. Degenerative or regenerative voltage which is fed back to circuits before its originating point; usually applied to a control anode of a tube or other device. 2. Voltage applied to a grid of a tube (or tubes) or electrode of another device to reduce a condition which has been upset by some external cause.


A type of vacuum-tube voltmeter in which the grid and cathode of a tube act as a diode rectifier, and the rectified grid voltage, amplified by the tube, operates a meter in the plate circuit.

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