Beam deflection tubes, sometimes known as sheet beam tubes, are

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...

s with an

electron gun An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode-ray tubes (CRTs), used in nearly ...

, a beam intensity control grid, a

screen grid A tetrode is a vacuum tube (called ''valve'' in British English) having four active electrodes. The four electrodes in order from the centre are: a thermionic cathode, first and second grids and a plate (called ''anode'' in British English). T ...

, sometimes a suppressor grid, and two

electrostatic deflection Electrostatic deflection refers to a way for modifying the path of a beam of charged particles by the use of an electric field applied transverse to the path of the particles. The technique is called electro''static'' because the strength and di ...

electrodes on opposite sides of the electron beam, that can direct the rectangular beam to either of two

anode An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic ...

s in the same plane. They can be used as two-quadrant, single-balanced mixers or (de)modulators with very linear qualities, their mode of operation similar to one-half of a Gilbert Cell, by applying an unbalanced signal to the control grid and a

balanced In telecommunications and professional audio, a balanced line or balanced signal pair is a circuit consisting of two conductors of the same type, both of which have equal impedances along their lengths and equal impedances to ground and to other ci ...

signal to the deflection electrodes, then extracting the balanced mixing products and from the two anodes. Similar to a

pentagrid converter The pentagrid converter is a type of radio receiving valve (vacuum tube) with five grids used as the frequency mixer stage of a superheterodyne radio receiver. The pentagrid was part of a line of development of valves that were able to take an ...

, the cathode and the first two grids can be made into an oscillator. Two beam deflection tubes can be combined to form a double-balanced mixer. They need extensive shielding against external magnetic fields. The ballistic deflection transistors currently under development employ a similar principle.

Examples

*6218/E80T - Modulated beam deflection tube, for pulse generation up to 375 MHz; single-anode version, shock-proof up to 500 g *7360 - Balanced modulator or product detector up to 100 MHz *6AR8, 6JH8, 6ME8 - Analog television chroma signal demodulators used in color TV receivers More elaborate applications of the principle include: * 2H21 and 5593 - Magnetically controlled "Phasitron" phase modulator tubes used in early FM broadcast transmitters. * 6090 - 18-channel analog

demultiplexer In electronics, a multiplexer (or mux; spelled sometimes as multiplexor), also known as a data selector, is a device that selects between several analog or digital input signals and forwards the selected input to a single output line. The sel ...

for telecomms receiving channel banks, an electrostatic deflection field determines which one out of 18 anodes receives the electron beam controlled by a common grid *6170 and 6324 - 25-channel analog multiplexer for telecomms transmitting channel banks, a rotating magnetic deflection field determines through which one out of 25 grids the electron beam passes to the common anode *6462 ''Magnetic pickup tube'', a 1-axis magnetometer with approx. resolution; the electron beam is electrostatically centered between two anodes while no magnetic field is present; the magnetic field to be detected will then deflect the beam more towards one of the anodes, resulting in an imbalance between the two anode currents * E1T - Trochotron with a fluorescent-screen readout * QK329 - '' Square-law tube'' for use as a

function generator In electrical engineering, a function generator is usually a piece of electronic test equipment or software used to generate different types of electrical waveforms over a wide range of frequencies. Some of the most common waveforms produced ...

analog computer An analog computer or analogue computer is a type of computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities (''analog signals'') to model the problem being solved. In ...

s. A flat sheet beam is deflected across the anode which is partially covered by a parabolically stenciled screen "grid" that acts as the tube's output. * Parallel-output PCM tube, an

analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...

with per-bit, vertical anode bars with perforations encoding the Gray code. A flat, horizontal sheet beam was then vertically deflected by the input analog signal across the perforated anode array, causing the digital representation of the analog signal to appear on the anodes. With two-axis deflection: * Serial-output PCM tube, an analog-to-digital converter with one anode having binary-encoding perforations. As in an oscilloscope, the beam was swept horizontally by a

sawtooth wave The sawtooth wave (or saw wave) is a kind of non-sinusoidal waveform. It is so named based on its resemblance to the teeth of a plain-toothed saw with a zero rake angle. A single sawtooth, or an intermittently triggered sawtooth, is called ...

at the sample rate while the vertical deflection was controlled by the input analog signal, causing the beam to pass through higher or lower portions of the perforated anode. The anode collected or passed the beam, producing current variations in binary code, one bit at a time. *CK1414 Character generator monoscope for

text mode Text mode is a computer display mode in which content is internally represented on a computer screen in terms of characters rather than individual pixels. Typically, the screen consists of a uniform rectangular grid of ''character cells'', each ...

video rendering in early computer monitors, with a square target having letters, digits and symbols patterned on it in a customer-supplied

8x8 8x8 Inc. is an American provider of Voice over IP products. Its products include cloud-based voice, contact center, video, mobile and unified communications for businesses. Since 2018, 8x8 manages Jitsi. History The company was founded in 1987 ...

or 8x12 array. An electron beam selects and scans a character, both by appropriate deflection, and generates an analog video signal. * 7828 ''Scan conversion tube'', an analog video standards transcoder consisting of a CRT/ camera tube combination. The CRT part does not write onto a phosphor, but onto a thin, dielectric target; the camera part reads the deposited charge pattern at a different scan rate from the back side of this target. The setup could also be used as a

genlock Genlock (generator locking) is a common technique where the video output of one source (or a specific reference signal from a signal generator) is used to synchronize other picture sources together. The aim in video applications is to ensure the ...

. *

Selectron tube The Selectron was an early form of digital computer memory developed by Jan A. Rajchman and his group at the Radio Corporation of America (RCA) under the direction of Vladimir K. Zworykin. It was a vacuum tube that stored digital data as elect ...

Storage tube Storage tubes are a class of cathode-ray tubes (CRTs) that are designed to hold an image for a long period of time, typically as long as power is supplied to the tube. A specialized type of storage tube, the Williams tube, was used as a main mem ...

Williams tube The Williams tube, or the Williams–Kilburn tube named after inventors Freddie Williams and Tom Kilburn, is an early form of computer memory. It was the first random-access digital storage device, and was used successfully in several early co ...

References

{{Thermionic valves Frequency mixers Vacuum tubes