In the years 1942-1944, the Radio Manufacturers Association used a descriptive nomenclature system for industrial, transmitting, and special-purpose
vacuum tubes
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 a ...
. The numbering scheme was distinct from both the numbering schemes used for standard receiving tubes, and the existing transmitting tube numbering systems used previously, such as the "800 series" numbers originated by RCA and adopted by many others.
The system assigned numbers with the base form "1A21", and this numbering scheme is occasionally referred to by tube collectors and historians as the "1A21 system".
The first digit of the type number was 1-9, providing a rough indication of the filament/heater power rating (and therefore the overall power handling capabilities) of the tube. The assigned numbers were as follows:
*1-- No filament/heater, or cold cathode device
*2-- Up to 10 W
*3-- 10-20 W
*4-- 20-50 W
*5-- 50-100 W
*6-- 100-200 W
*7-- 200-500 W
*8-- 500W-1 kW
*9-- More than 1 kW
The second character was a letter broadly identifying the class of tube:
*A-- Single element (
ballast
Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship, ...
,
barretter)
*B-- Two-element device such as:
**
Diode
A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other.
A diode ...
**Transmit/receive tube (TR cell), cold-cathode water vapor discharge tube for use in
radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
systems, shorts the receiver input to protect it while the transmitter operates
**Anti-transmit/receive tube (ATR cell), cold-cathode water vapor discharge tube for use in radar systems, decouples the transmitter from the antenna while not operating, to prevent it from wasting received energy
**
Spark gap
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conduct ...
*C--
Triode
A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's 19 ...
*D--
Tetrode
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). Th ...
*E--
Pentode
A pentode is an electronic device having five electrodes. The term most commonly applies to a three-grid amplifying vacuum tube or thermionic valve that was invented by Gilles Holst and Bernhard D.H. Tellegen in 1926. The pentode (called a ''tripl ...
or beam power tetrode
*F--
Hexode
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 ...
*G-- Heptode
*H-- Octode
*J-- Magnetically controlled types, usually incorporating a resonator (essentially,
magnetron
The cavity magnetron is a high-power vacuum tube used in early radar systems and currently in microwave ovens and linear particle accelerators. It generates microwaves using the interaction of a stream of electrons with a magnetic field while ...
s)
*K-- Electrostatically controlled types, including a resonator (
klystron
A klystron is a specialized linear-beam vacuum tube, invented in 1937 by American electrical engineers Russell and Sigurd Varian,Pond, Norman H. "The Tube Guys". Russ Cochran, 2008 p.31-40 which is used as an amplifier for high radio frequenci ...
s and
inductive output tube
The inductive output tube (IOT) or klystrode is a variety of linear-beam vacuum tube, similar to a klystron, used as a power amplifier for high frequency radio waves. It evolved in the 1980s to meet increasing efficiency requirements for high-po ...
s)
*L--
Vacuum capacitor
A vacuum variable capacitor is a variable capacitor which uses a high vacuum as the dielectric instead of air or other insulating material. This allows for a higher voltage rating than an air dielectric using a smaller total volume. However, many ...
s
*N-- Crystal
rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an Power ...
s (This designation lived on as the "N" in the
EIA Eia or EIA may refer to:
Medicine
* Enzyme immunoassay
* Equine infectious anemia
* Exercise-induced anaphylaxis
* Exercise-induced asthma
* External iliac artery
Transport
* Edmonton International Airport, in Alberta, Canada
* Erbil Internation ...
/
JEDEC
The JEDEC Solid State Technology Association is an independent semiconductor engineering trade organization and standardization body headquartered in Arlington County, Virginia, United States.
JEDEC has over 300 members, including some of the w ...
''EIA-370'' solid state device numbers standard, like
2N2222
The 2N2222 is a common NPN bipolar junction transistor (BJT) used for general purpose low-power amplifying or switching applications. It is designed for low to medium current, low power, medium voltage, and can operate at moderately high spee ...
)
*P-- Photosensitive types (
phototube
A phototube or photoelectric cell is a type of gas-filled or vacuum tube that is sensitive to light. Such a tube is more correctly called a 'photoemissive cell' to distinguish it from photovoltaic or photoconductive cells. Phototubes were previ ...
s,
photomultiplier A photomultiplier is a device that converts incident photons into an electrical signal.
Kinds of photomultiplier include:
* Photomultiplier tube, a vacuum tube converting incident photons into an electric signal. Photomultiplier tubes (PMTs for sho ...
s,
camera tubes,
image converters)
*Q-- Resonant vacuum cavities
*R--
Ignitron
An ignitron is a type of gas-filled tube used as a controlled rectifier and dating from the 1930s. Invented by Joseph Slepian while employed by Westinghouse, Westinghouse was the original manufacturer and owned trademark rights to the name "Ignit ...
s and
mercury arc rectifier
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Mercury ...
s
*S-- Vacuum switches
*T
Storage, radial beam, and
deflection control tubes (no known examples assigned)
*V--
Flash tube
Flash, flashes, or FLASH may refer to:
Arts, entertainment, and media
Fictional aliases
* Flash (DC Comics character), several DC Comics superheroes with super speed:
** Flash (Barry Allen)
** Flash (Jay Garrick)
** Wally West, the first Kid F ...
s
*W--
Travelling wave tube
A traveling-wave tube (TWT, pronounced "twit") or traveling-wave tube amplifier (TWTA, pronounced "tweeta") is a specialized vacuum tube that is used in electronics to amplify radio frequency (RF) signals in the microwave range. The TWT belongs t ...
*X--
X-ray tube
An X-ray tube is a vacuum tube that converts electrical input power into X-rays. The availability of this controllable source of X-rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. In contrast ...
*Y--
Thermionic converter
A thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. Caesium vapor is used to optimize the electrode work functi ...
The last 2 digits were serially assigned, beginning with 21 to avoid possible confusion with receiving tubes or CRT phosphor designations.
Multiple section tubes (like the 3E29 or 8D21) are assigned a letter corresponding to ONE set of electrodes.
Oddities
Like all tube numbering systems, there are many inconsistencies between theory and practice. For example, there is no assigned letter code for cathode-ray tubes. Some unusual types received rather mundane sounding designations, based solely on electrode count, because there was no better place to put them. For example, the 2F21 is not an actual hexode, but a pattern generating monoscope tube. Some very exotic types received generic designators, even when there was a more appropriate designator available. For example, the 2H21 "phasitron" phase modulator tube used in early FM broadcast transmitters was assigned an "H" (octode) designator, when it would have been a perfect candidate for the otherwise unused "T" category for deflection controlled tubes.
The first-digit filament/heater power rating confusingly gathers valves of widely-differing ratings. The 2G21 is a subminiature Triode-Hexode, with a maximum anode (plate) current of some 0.2 milliamps and a maximum voltage of 45 volts. The 2J42 Magnetron, with a power output of some 7 kilowatts, is rated for anode current of 4.5 amps (pulse peak) at anode voltage of 5,500 volts.
Famous types
Many of the "1A21" series are well known to collectors and restorers of WW2 vintage radio equipment. A short list of well-known or historic types numbered under this system:
*1N23—Silicon point contact diode used in early radar mixers.
*1P25—Infrared image converter used in WW2
night vision
Night vision is the ability to see in low-light conditions, either naturally with scotopic vision or through a night-vision device. Night vision requires both sufficient spectral range and sufficient intensity range. Humans have poor night vi ...
"sniperscopes".
*2C39--"Oilcan" type planar triode.
*2C43--"Lighthouse" type planar triode.
*2D21—Miniature glass tetrode thyratron used in jukeboxes and computer equipment.
*2P23—Early image
orthicon
Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...
TV camera tube.
*3B28—Xenon half wave rectifier—ruggedized replacement for mercury vapor type 866.
*3E29—Dual beam power tube used in radar equipment—a pulse rated variant of the earlier 829B.
*4D21—VHF beam tetrode better known by
Eimac Eimac is a trade mark of Eimac Products, part of the Microwave Power Products Division of Communications & Power Industries. It produces power vacuum tubes for radio frequency applications such as broadcast and radar transmitters. The company name ...
commercial number 4-125A.
*5C22—Hydrogen
thyratron
A thyratron is a type of gas-filled tube used as a high-power electrical switch and controlled rectifier. Thyratrons can handle much greater currents than similar hard-vacuum tubes. Electron multiplication occurs when the gas becomes ionized, pro ...
for radar modulators.
*6C21—Triode radar modulator for "hard tube" pulsers.
*8D21—Internally water cooled dual tetrode used in early VHF TV transmitters.
This numbering system was abandoned in 1944 in favor of a non-descriptive numbering system of 4 digit numbers beginning with 5500. This new system persisted until the final days of tubes, with type numbers registered up into the 9000 series.
References
*Sibley, Ludwell "Tube Lore--A reference for Users and Collectors", 1st edition, 1996
See also
*
List of vacuum tubes
This is a list of vacuum tubes or ''thermionic valves'', and low-pressure gas-filled tubes, or ''discharge tubes''. Before the advent of semiconductor devices, thousands of tube types were used in consumer electronics. Many industrial, military or ...
*
RETMA tube designation The Radio Electronics Television Manufacturers' Association was formed in 1953, as a result of mergers with other trade standards organisations, such as the RMA. It was principally responsible for the standardised nomenclature for American vacuum t ...
*
Mullard–Philips tube designation In Europe, the principal method of numbering vacuum tubes ("thermionic valves") was the nomenclature used by the Philips company and its subsidiaries Mullard in the UK, Valvo( de, it) in Germany, Radiotechnique (''Miniwatt-Dario'' b ...
*
Russian tube designations Vacuum tubes produced in the former Soviet Union and in present-day Russia carry their own unique designations. Some confusion has been created in "translating" these designations, as they use Cyrillic rather than Latin characters.
1929 system
T ...
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