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138-568: In the early 1950s transistors had not yet replaced vacuum tubes in most electronics. Tubes varied widely in their actual characteristics from tube to tube even of the same model. Engineers had developed techniques to ensure that the overall circuit was not overly sensitive to these changes so they could be replaced without causing trouble. The same techniques had not yet been developed for transistor-based systems, they were simply too new. While smaller circuits could be "hand tuned" to work, larger systems using many transistors were not well understood. At

276-556: A memory drum . Normally the memory for a machine would be built up by stacking a number of core assemblies, or "planes", each one holding a single bit of the machine's word. For instance, with a 40-bit word as in the DRTE, the system would use 40 planes of core. Addresses would be looked up by translating each 10-bit address into an X and Y address in the planes; for 1,024 words in the DTRE this needed 32×32 planes. One problem with using core on

414-405: A "1". The small amount of energy used to do this causes a pulse to be output on a different wire, the read line. So to read data, you write "1" to that location, if a pulse is seen on the read line the location originally held "0", and no pulse means it held "1". One problem with this system is that other cores on the same lines (X or Y) will give off a very small signal as well, potentially masking

552-494: A DC power supply , as a demodulator of amplitude modulated (AM) radio signals and for similar functions. Early tubes used the filament as the cathode; this is called a "directly heated" tube. Most modern tubes are "indirectly heated" by a "heater" element inside a metal tube that is the cathode. The heater is electrically isolated from the surrounding cathode and simply serves to heat the cathode sufficiently for thermionic emission of electrons. The electrical isolation allows all

690-453: A backup to their own much simpler design. In the end the US design ran into lengthy delays, and the "too advanced" Canadian design was eventually launched in 1962 as Alouette I . While Alouette was being designed, a major question about the lifetime of the solar cells powering the system came to be solved on the DRTE computer. They developed a program that simulated the effects of precession on

828-649: A blue glow. Finnish inventor Eric Tigerstedt significantly improved on the original triode design in 1914, while working on his sound-on-film process in Berlin, Germany. Tigerstedt's innovation was to make the electrodes concentric cylinders with the cathode at the centre, thus greatly increasing the collection of emitted electrons at the anode. Irving Langmuir at the General Electric research laboratory ( Schenectady, New York ) had improved Wolfgang Gaede 's high-vacuum diffusion pump and used it to settle

966-717: A cathode-ray tube known as the output device, just as on the Baby from which the Mark 1 had been developed. However, the Final Specification machine, completed in October 1949, benefitted from the addition of a teleprinter with a five-hole paper-tape reader and punch . Mathematician Alan Turing , who had been appointed to the nominal post of Deputy Director of the Computing Machine Laboratory at

1104-501: A combination of a triode with a hexode and even an octode have been used for this purpose. The additional grids include control grids (at a low potential) and screen grids (at a high voltage). Many designs use such a screen grid as an additional anode to provide feedback for the oscillator function, whose current adds to that of the incoming radio frequency signal. The pentagrid converter thus became widely used in AM receivers, including

1242-402: A complex system was to build a computer. This was not something they needed for their own use at the time, it was simply an example of an extremely complex system that would test their capabilities like few other systems could. But as development continued, many of the engineers involved became more interested in computer design than electronics. This was outside the DRTE's charter and eventually

1380-586: A far superior and versatile technology for use in radio transmitters and receivers. At the end of the 19th century, radio or wireless technology was in an early stage of development and the Marconi Company was engaged in development and construction of radio communication systems. Guglielmo Marconi appointed English physicist John Ambrose Fleming as scientific advisor in 1899. Fleming had been engaged as scientific advisor to Edison Telephone (1879), as scientific advisor at Edison Electric Light (1882), and

1518-402: A few of the standard encodings; for instance, 00000 and 01000, which mean "no effect" and "linefeed" in the teleprinter code, were represented by the characters "/" and "@" respectively. Binary zero, represented by the forward slash, was the most common character in programs and data, leading to sequences written as "///////////////". One early user suggested that Turing's choice of a forward slash

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1656-505: A gas, typically at low pressure, which exploit phenomena related to electric discharge in gases , usually without a heater. One classification of thermionic vacuum tubes is by the number of active electrodes . A device with two active elements is a diode , usually used for rectification . Devices with three elements are triodes used for amplification and switching . Additional electrodes create tetrodes , pentodes , and so forth, which have multiple additional functions made possible by

1794-473: A government contract with the local firm of Ferranti to make a commercial version of the machine, the Ferranti Mark 1. In his letter to the company, dated 26 October 1948, Lockspeiser authorised the company to "proceed on the lines we discussed, namely, to construct an electronic calculating machine to the instructions of Professor F. C. Williams". From that point on, development of the Mark 1 had

1932-425: A greater number of "downstream" circuits without additional amplifiers. The overall effect was to reduce, sometimes greatly, the total number of transistors needed to implement a digital circuit. Moody published his circuit in 1956. One downside, only realized later, is that the current draw of Moody's flip-flop was not balanced, so storing different numbers in them could lead to dramatically different current needs on

2070-431: A heated electron-emitting cathode and an anode. Electrons can flow in only one direction through the device – from the cathode to the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grids. These devices became a key component of electronic circuits for the first half of the twentieth century. They were crucial to

2208-400: A low potential space charge region between the anode and screen grid to return anode secondary emission electrons to the anode when the anode potential is less than that of the screen grid. Formation of beams also reduces screen grid current. In some cylindrically symmetrical beam power tubes, the cathode is formed of narrow strips of emitting material that are aligned with the apertures of

2346-497: A machine can write a sonnet or compose a concerto because of thoughts and emotions felt, and not by the chance fall of symbols, could we agree that machine equals brain – that is, not only write it but know that it had written it. No machine could feel pleasure at its success, grief when its valves fuse, be warmed by flattery, be made miserable by its mistakes, be charmed by sex, be angry or miserable when it cannot get what it wants. The Times reported on Jefferson's speech

2484-613: A new machine that would include a floating point unit . Work began in 1951, and the resulting machine, which ran its first program in May 1954, was known as Meg, or the megacycle machine. It was smaller and simpler than the Mark 1, and much faster for maths problems. Ferranti produced a version of Meg with the Williams tubes replaced by the more reliable core memory , marketed as the Ferranti Mercury . The successful operation of

2622-413: A new type of flip-flop circuit, a key component of all computer systems. Moody's design used a P-N-P-N junction , consisting of a PNP and NPN transistor connected back-to-back. Most machines of the era used Eccles-Jordan flip-flops; this was originally a tube-based concept that was being used by replacing the tubes with transistors. The P-N-P-N circuit offered much higher power output, allowing it to drive

2760-432: A number of truly massive machines had been built, like SAGE , most machines were much smaller in order to improve uptime. With transistors this limitation was removed; more complex machines could be built with little effect on reliability, as long as one was willing to pay the price for more transistors. With the price of transistors falling all the time, Florida's design included every feature he imagined would be useful in

2898-414: A pair of beam deflection electrodes which deflected the current towards either of two anodes. They were sometimes known as the 'sheet beam' tubes and used in some color TV sets for color demodulation . The similar 7360 was popular as a balanced SSB (de)modulator . A beam tetrode (or "beam power tube") forms the electron stream from the cathode into multiple partially collimated beams to produce

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3036-460: A plane at a time and then wired together, whereas this method required the entire core to be built before the read wires could be added. The only major downside to the design is that it required more power to run. I/O device on the DRTE design were extremely limited, consisting of a Flexowriter for output, and a paper tape reader at about 600 CPS for input. In particular, the system added a hardware binary-to-decimal/decimal-to-binary converter that

3174-412: A printing instrument was needed. As a result of experiments conducted on Edison effect bulbs, Fleming developed a vacuum tube that he termed the oscillation valve because it passed current in only one direction. The cathode was a carbon lamp filament, heated by passing current through it, that produced thermionic emission of electrons. Electrons that had been emitted from the cathode were attracted to

3312-638: A program to read sequentially through an array of words in memory. Thirty-four patents resulted from the machine's development, and many of the ideas behind its design were incorporated in subsequent commercial products such as the IBM 701 and 702 as well as the Ferranti Mark 1. The chief designers, Frederic C. Williams and Tom Kilburn , concluded from their experiences with the Mark ;1 that computers would be used more in scientific roles than in pure mathematics. In 1951, they started development work on Meg ,

3450-509: A relatively low-value resistor is connected between the cathode and ground. This makes the cathode positive with respect to the grid, which is at ground potential for DC. However C batteries continued to be included in some equipment even when the "A" and "B" batteries had been replaced by power from the AC mains. That was possible because there was essentially no current draw on these batteries; they could thus last for many years (often longer than all

3588-434: A scientific machine. In particular, the design ultimately included a number of subsystems for input/output , a hardware binary/decimal converter, floating-point hardware including a square root function, a number of loop instructions and index registers to support them, and used a complex three-address instruction format . The three-address system meant that every instruction included the address of up to two operands and

3726-407: A simple oscillator only requiring connection of the plate to a resonant LC circuit to oscillate. The dynatron oscillator operated on the same principle of negative resistance as the tunnel diode oscillator many years later. The dynatron region of the screen grid tube was eliminated by adding a grid between the screen grid and the plate to create the pentode . The suppressor grid of the pentode

3864-419: A small-signal vacuum tube are 1 to 10 millisiemens. It is one of the three 'constants' of a vacuum tube, the other two being its gain μ and plate resistance R p or R a . The Van der Bijl equation defines their relationship as follows: g m = μ R p {\displaystyle g_{m}={\mu \over R_{p}}} The non-linear operating characteristic of

4002-462: A source of friction between the group and the DRB who funded them. Starting about 1955, David Florida drove the development of a computer using Moody's flip-flop design. He examined existing computer designs and concluded that the main limitation in computer complexity was due largely to the burnout rate of the tubes; a more powerful design required more tubes, which meant more frequent burnouts. Although

4140-517: A suitable memory device. The University of Manchester 's Baby , the world's first electronic stored-program computer, had successfully demonstrated the practicality of the stored-program approach and of the Williams tube , an early form of computer memory based on a standard cathode-ray tube (CRT), by running its first program on 21 June 1948. Early electronic computers were generally programmed by being rewired, or via plugs and patch panels ; there

4278-405: A vacuum phototube , however, achieve electron emission through the photoelectric effect , and are used for such purposes as the detection of light intensities. In both types, the electrons are accelerated from the cathode to the anode by the electric field in the tube. The simplest vacuum tube, the diode (i.e. Fleming valve ), was invented in 1904 by John Ambrose Fleming . It contains only

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4416-456: A vacuum where electron emission from the cathode depends on energy from photons rather than thermionic emission ). A vacuum tube consists of two or more electrodes in a vacuum inside an airtight envelope. Most tubes have glass envelopes with a glass-to-metal seal based on kovar sealable borosilicate glasses , although ceramic and metal envelopes (atop insulating bases) have been used. The electrodes are attached to leads which pass through

4554-400: A very high plate voltage away from lower voltages, and accommodating one more electrode than allowed by the base. There was even an occasional design that had two top cap connections. The earliest vacuum tubes evolved from incandescent light bulbs , containing a filament sealed in an evacuated glass envelope. When hot, the filament in a vacuum tube (a cathode ) releases electrons into

4692-429: A wide range of frequencies. To combat the stability problems of the triode as a radio frequency amplifier due to grid-to-plate capacitance, the physicist Walter H. Schottky invented the tetrode or screen grid tube in 1919. He showed that the addition of an electrostatic shield between the control grid and the plate could solve the problem. This design was refined by Hull and Williams. The added grid became known as

4830-445: Is a current . Compare this to the behavior of the bipolar junction transistor , in which the controlling signal is a current and the output is also a current. For vacuum tubes, transconductance or mutual conductance ( g m ) is defined as the change in the plate(anode)/cathode current divided by the corresponding change in the grid to cathode voltage, with a constant plate(anode) to cathode voltage. Typical values of g m for

4968-406: 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 thermionic tube or thermionic valve utilizes thermionic emission of electrons from a hot cathode for fundamental electronic functions such as signal amplification and current rectification . Non-thermionic types such as

5106-469: Is not heated and does not emit electrons. The filament has a dual function: it emits electrons when heated; and, together with the plate, it creates an electric field due to the potential difference between them. Such a tube with only two electrodes is termed a diode , and is used for rectification . Since current can only pass in one direction, such a diode (or rectifier ) will convert alternating current (AC) to pulsating DC. Diodes can therefore be used in

5244-410: Is not important since they are simply re-captured by the plate. But in a tetrode they can be captured by the screen grid since it is also at a positive voltage, robbing them from the plate current and reducing the amplification of the tube. Since secondary electrons can outnumber the primary electrons over a certain range of plate voltages, the plate current can decrease with increasing plate voltage. This

5382-564: Is the Loewe 3NF . This 1920s device has three triodes in a single glass envelope together with all the fixed capacitors and resistors required to make a complete radio receiver. As the Loewe set had only one tube socket, it was able to substantially undercut the competition, since, in Germany, state tax was levied by the number of sockets. However, reliability was compromised, and production costs for

5520-416: Is the dynatron region or tetrode kink and is an example of negative resistance which can itself cause instability. Another undesirable consequence of secondary emission is that screen current is increased, which may cause the screen to exceed its power rating. The otherwise undesirable negative resistance region of the plate characteristic was exploited with the dynatron oscillator circuit to produce

5658-564: The Edison effect , that became well known. Although Edison was aware of the unidirectional property of current flow between the filament and the anode, his interest (and patent ) concentrated on the sensitivity of the anode current to the current through the filament (and thus filament temperature). It was years later that John Ambrose Fleming applied the rectifying property of the Edison effect to detection of radio signals, as an improvement over

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5796-684: The plate ( anode ) when the plate was at a positive voltage with respect to the cathode. Electrons could not pass in the reverse direction because the plate was not heated and not capable of thermionic emission of electrons. Fleming filed a patent for these tubes, assigned to the Marconi company, in the UK in November 1904 and this patent was issued in September 1905. Later known as the Fleming valve ,

5934-429: The screen grid or shield grid . The screen grid is operated at a positive voltage significantly less than the plate voltage and it is bypassed to ground with a capacitor of low impedance at the frequencies to be amplified. This arrangement substantially decouples the plate and the control grid , eliminating the need for neutralizing circuitry at medium wave broadcast frequencies. The screen grid also largely reduces

6072-480: The 6GH8 /ECF82 triode-pentode, quite popular in television receivers. The desire to include even more functions in one envelope resulted in the General Electric Compactron which has 12 pins. A typical example, the 6AG11, contains two triodes and two diodes. Some otherwise conventional tubes do not fall into standard categories; the 6AR8, 6JH8 and 6ME8 have several common grids, followed by

6210-482: The 6SN7 , is a "dual triode" which performs the functions of two triode tubes while taking up half as much space and costing less. The 12AX7 is a dual "high mu" (high voltage gain ) triode in a miniature enclosure, and became widely used in audio signal amplifiers, instruments, and guitar amplifiers . The introduction of the miniature tube base (see below) which can have 9 pins, more than previously available, allowed other multi-section tubes to be introduced, such as

6348-632: The Colonel Bogey March by attaching a speaker to a particular flip-flop. In the late 1950s the US was in the midst of rolling out the SAGE system, and became interested in the effects of aurora borealis on radar operation. An agreement was eventually signed between the DRB and US Air Force , with the Air Force providing two million dollars to build a radar research center modelled on MIT 's Lincoln Laboratory , which had provided much of

6486-474: The instruction code , which allowed for 1,024 (2 ) different instructions. The machine had 26 initially, increasing to 30 when the function codes to programmatically control the data transfer between the magnetic drum and the cathode-ray tube (CRT) main store were added. On the Intermediary Version programs were input by key switches, and the output was displayed as a series of dots and dashes on

6624-487: The junction field-effect transistor (JFET), although vacuum tubes typically operate at over a hundred volts, unlike most semiconductors in most applications. The 19th century saw increasing research with evacuated tubes, such as the Geissler and Crookes tubes . The many scientists and inventors who experimented with such tubes include Thomas Edison , Eugen Goldstein , Nikola Tesla , and Johann Wilhelm Hittorf . With

6762-467: The magnetic detector . Amplification by vacuum tube became practical only with Lee de Forest 's 1907 invention of the three-terminal " audion " tube, a crude form of what was to become the triode . Being essentially the first electronic amplifier , such tubes were instrumental in long-distance telephony (such as the first coast-to-coast telephone line in the US) and public address systems , and introduced

6900-482: The 1940s, Turing and others such as Konrad Zuse developed the idea of using the computer's own memory to hold both the program and data, instead of tape, but it was mathematician John von Neumann who became widely credited with defining that stored-program computer architecture , on which the Manchester Mark 1 was based. The practical construction of a von Neumann computer depended on the availability of

7038-413: The 19th century, telegraph and telephone engineers had recognized the need to extend the distance that signals could be transmitted. In 1906, Robert von Lieben filed for a patent for a cathode-ray tube which used an external magnetic deflection coil and was intended for use as an amplifier in telephony equipment. This von Lieben magnetic deflection tube was not a successful amplifier, however, because of

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7176-485: The Audion for demonstration to AT&T's engineering department. Dr. Harold D. Arnold of AT&T recognized that the blue glow was caused by ionized gas. Arnold recommended that AT&T purchase the patent, and AT&T followed his recommendation. Arnold developed high-vacuum tubes which were tested in the summer of 1913 on AT&T's long-distance network. The high-vacuum tubes could operate at high plate voltages without

7314-468: The Baby was intensively developed as a prototype for the Manchester Mark 1, initially with the aim of providing the university with a more realistic computing facility. In October 1948, UK Government Chief Scientist Ben Lockspeiser was given a demonstration of the prototype Mark 1 while on a visit to the University of Manchester. Lockspeiser was so impressed by what he saw that he immediately initiated

7452-427: The DRTE computer were put on DAR instead. The machine itself consisted of a non-programmable computer that read the data into 40,000 bits of core memory, tagged it with timecode and other information, and then wrote it to magnetic tape . DAR was used for a number of years, and had to be rebuilt after a fire in 1962. In 1958 the DRB sent a proposal to NASA to launch a "topside sounder", which would take measurements of

7590-427: The DRTE machine was that core required fairly high power in order to operate. Providing such power from transistors, which at the time were low-power only, represented a major challenge. Although one solution, commonly used at the time, was to build the core machinery out of tubes, for the DRTE machine this was considered one more challenge in transistor design. The eventual solution, designed primarily by Richard Cobbald,

7728-541: The Earth's ionosphere from space. This was a topic of some importance at the time; the DRB was conducting a major ionospheric research program in order to build a very-long-distance communications system (which would later be used on the Mid-Canada Line and DEW Line ). The various US agencies that commented on the system were highly sceptical that the DRB could build such a device, but suggested they do so anyway as

7866-568: The Electronics Lab became a major center of excellence in the field of transistors, and through an outreach program, the Electronic Component Research and Development Committee , were able to pass on their knowledge to visiting engineers from major Canadian electronics firms who were entering the transistor field. The key development that led to the eventual construction of the computer was Moody's invention of

8004-548: The Manchester Mark 1 and its predecessor, the Baby, was widely reported in the British press, which used the phrase "electronic brain" to describe the machines. Lord Louis Mountbatten had earlier introduced that term in a speech delivered to the British Institution of Radio Engineers on 31 October 1946, in which he speculated about how the primitive computers then available might evolve. The excitement surrounding

8142-577: The Mark 1's successor, which would include a floating point unit . It was also called the Manchester Automatic Digital Machine , or MADM . In 1936, mathematician Alan Turing published a definition of a theoretical "universal computing machine", a computer which held its program on tape, along with the data being worked on. Turing proved that such a machine was capable of solving any conceivable mathematical problem for which an algorithm could be written. During

8280-496: The US technical lead in radar systems. The DRB proposed a site between five and six hundred miles from the Churchill Rocket Research Range , which was already being used for extensive aurora research with their rocketry program. Such a location would allow the radars to directly measure the effects of aurora on radar by tracking the rocket launches. Eventually a site outside Prince Albert, Saskatchewan

8418-421: The University of Manchester in September 1948, devised a base 32 encoding scheme based on the standard ITA2 5-bit teleprinter code, which allowed programs and data to be written to and read from paper tape. The ITA2 system maps each of the possible 32 binary values that can be represented in 5 bits (2 ) to a single character. Thus "10010" represents "D", "10001" represents "Z", and so forth. Turing changed only

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8556-462: The additional controllable electrodes. Other classifications are: Vacuum tubes may have other components and functions than those described above, and are described elsewhere. These include as cathode-ray tubes , which create a beam of electrons for display purposes (such as the television picture tube, in electron microscopy , and in electron beam lithography ); X-ray tubes ; phototubes and photomultipliers (which rely on electron flow through

8694-610: The additional purpose of supplying Ferranti with a design on which to base their commercial machine. The government's contract with Ferranti ran for five years from November 1948, and involved an estimated £35,000 per year (equivalent to £1.38 million per year in 2023). The Baby had been designed by the team of Frederic C. Williams , Tom Kilburn and Geoff Tootill . To develop the Mark 1 they were joined by two research students, D. B. G. Edwards and G. E. Thomas; work began in earnest in August 1948. The project soon had

8832-826: The addresses of two parameters and a result, would make programming easier than a register-based system. An experimental version of the machine consisted of the basic math unit and memory handling. Construction of the complete system started in 1958 and was completed in 1960. The machine ran on a 5 microseconds/cycle lock, or 200 kHz, fairly competitive for a machine of the era. A floating point add took between 50 and 365 microseconds (μS). The longest instructions, divide or square root, took 5.3 milliseconds (ms) for floating point. Integer adds took about 200 μS, but other operations were handled in subroutines as opposed to hardware and took much longer; an integer division/square root required 8.2 ms for instance. The computer used core memory for all storage, lacking "secondary" systems such as

8970-400: The allied military by 1916. Historically, vacuum levels in production vacuum tubes typically ranged from 10 μPa down to 10 nPa (8 × 10   Torr down to 8 × 10  Torr). The triode and its derivatives (tetrodes and pentodes) are transconductance devices, in which the controlling signal applied to the grid is a voltage , and the resulting amplified signal appearing at the anode

9108-435: The anode, cathode, and one grid, and so on. The first grid, known as the control grid, (and sometimes other grids) transforms the diode into a voltage-controlled device : the voltage applied to the control grid affects the current between the cathode and the plate. When held negative with respect to the cathode, the control grid creates an electric field that repels electrons emitted by the cathode, thus reducing or even stopping

9246-677: The average size of the design team working on the Mark 1 and its predecessor, the Baby, had been about four people. During that time 34 patents were taken out based on the team's work, either by the Ministry of Supply or by its successor, the National Research Development Corporation . In July 1949, IBM invited Williams to the United States on an all-expenses-paid trip to discuss the Mark 1's design. The company subsequently licensed several of

9384-479: The base terminals, some tubes had an electrode terminating at a top cap . The principal reason for doing this was to avoid leakage resistance through the tube base, particularly for the high impedance grid input. The bases were commonly made with phenolic insulation which performs poorly as an insulator in humid conditions. Other reasons for using a top cap include improving stability by reducing grid-to-anode capacitance, improved high-frequency performance, keeping

9522-404: The cathode slam into the anode (plate) and heat it; this can occur even in an idle amplifier due to the quiescent current necessary to ensure linearity and low distortion. In a power amplifier, this heating can be considerable and can destroy the tube if driven beyond its safe limits. Since the tube contains a vacuum, the anodes in most small and medium power tubes are cooled by radiation through

9660-536: The cathode, no direct current could pass from the cathode to the grid. Thus a change of voltage applied to the grid, requiring very little power input to the grid, could make a change in the plate current and could lead to a much larger voltage change at the plate; the result was voltage and power amplification . In 1908, de Forest was granted a patent ( U.S. patent 879,532 ) for such a three-electrode version of his original Audion for use as an electronic amplifier in radio communications. This eventually became known as

9798-428: The control grid, reducing control grid current. This design helps to overcome some of the practical barriers to designing high-power, high-efficiency power tubes. Manufacturer's data sheets often use the terms beam pentode or beam power pentode instead of beam power tube , and use a pentode graphic symbol instead of a graphic symbol showing beam forming plates. Manchester Mark 1 The Manchester Mark 1

9936-411: The cost of wiring core. Cobbald's design made what in retrospect seems like an obvious change; the read wire was threaded across the planes instead of one per plane. In this system the read wire really did pass through only one set of powered lines, and the problems of the "extra signal" were avoided completely. It is not entirely surprising that this solution was not hit on before; cores were constructed

10074-400: The current between cathode and anode. As long as the control grid is negative relative to the cathode, essentially no current flows into it, yet a change of several volts on the control grid is sufficient to make a large difference in the plate current, possibly changing the output by hundreds of volts (depending on the circuit). The solid-state device which operates most like the pentode tube is

10212-428: The development of radio , television , radar , sound recording and reproduction , long-distance telephone networks, and analog and early digital computers . Although some applications had used earlier technologies such as the spark gap transmitter for radio or mechanical computers for computing, it was the invention of the thermionic vacuum tube that made these technologies widespread and practical, and created

10350-445: The discipline of electronics . In the 1940s, the invention of semiconductor devices made it possible to produce solid-state devices, which are smaller, safer, cooler, and more efficient, reliable, durable, and economical than thermionic tubes. Beginning in the mid-1960s, thermionic tubes were being replaced by the transistor . However, the cathode-ray tube (CRT) remained the basis for television monitors and oscilloscopes until

10488-491: The drum took 30  milliseconds , during which time both pages could be transferred to the CRT main memory, although the actual data transfer time depended on the latency, the time it took for a page to arrive under the read/write head. Writing pages to the drum took about twice as long as reading. The drum's rotational speed was synchronised to the main central processor clock , which allowed for additional drums to be added. Data

10626-518: The dual purpose of supplying Ferranti with a working design on which they could base a commercial machine, the Ferranti Mark 1, and of building a computer that would allow researchers to gain experience of how such a machine could be used in practice. The first of the two versions of the Manchester Mark 1 – known as the Intermediary Version ;– was operational by April 1949. However, this first version lacked features such as

10764-546: The early 21st century. Thermionic tubes are still employed in some applications, such as the magnetron used in microwave ovens, certain high-frequency amplifiers , and high end audio amplifiers, which many audio enthusiasts prefer for their "warmer" tube sound , and amplifiers for electric musical instruments such as guitars (for desired effects, such as "overdriving" them to achieve a certain sound or tone). Not all electronic circuit valves or electron tubes are vacuum tubes. Gas-filled tubes are similar devices, but containing

10902-417: The envelope via an airtight seal. Most vacuum tubes have a limited lifetime, due to the filament or heater burning out or other failure modes, so they are made as replaceable units; the electrode leads connect to pins on the tube's base which plug into a tube socket . Tubes were a frequent cause of failure in electronic equipment, and consumers were expected to be able to replace tubes themselves. In addition to

11040-425: The exception of early light bulbs , such tubes were only used in scientific research or as novelties. The groundwork laid by these scientists and inventors, however, was critical to the development of subsequent vacuum tube technology. Although thermionic emission was originally reported in 1873 by Frederick Guthrie , it was Thomas Edison's apparently independent discovery of the phenomenon in 1883, referred to as

11178-419: The filament and cathode. Except for diodes, additional electrodes are positioned between the cathode and the plate (anode). These electrodes are referred to as grids as they are not solid electrodes but sparse elements through which electrons can pass on their way to the plate. The vacuum tube is then known as a triode , tetrode , pentode , etc., depending on the number of grids. A triode has three electrodes:

11316-543: The following day, adding that Jefferson forecast that "the day would never dawn when the gracious rooms of the Royal Society would be converted into garages to house these new fellows". This was interpreted as a deliberate slight to Newman, who had secured a grant from the society to continue the work of the Manchester team. In response Newman wrote a follow-up article for The Times , in which he claimed that there

11454-444: The glass envelope. In some special high power applications, the anode forms part of the vacuum envelope to conduct heat to an external heat sink, usually cooled by a blower, or water-jacket. Klystrons and magnetrons often operate their anodes (called collectors in klystrons) at ground potential to facilitate cooling, particularly with water, without high-voltage insulation. These tubes instead operate with high negative voltages on

11592-411: The influence of the plate voltage on the space charge near the cathode, permitting the tetrode to produce greater voltage gain than the triode in amplifier circuits. While the amplification factors of typical triodes commonly range from below ten to around 100, tetrode amplification factors of 500 are common. Consequently, higher voltage gains from a single tube amplification stage became possible, reducing

11730-488: The instructions necessary to programmatically transfer data between the main store and its newly developed magnetic backing store, which had to be done by halting the machine and manually initiating the transfer. These missing features were incorporated in the Final Specification version, which was fully working by October 1949. The machine contained 4,050 valves and had a power consumption of 25 kilowatts . To increase reliability, purpose-built CRTs made by GEC were used in

11868-445: The machine instead of the standard devices used in the Baby. The Baby's 32-bit word length was increased to 40 bits . Each word could hold either one 40-bit number or two 20-bit program instructions. The main store initially consisted of two double-density Williams tubes, each holding two arrays of 32 x 40-bit words  – known as pages  – backed up by a magnetic drum capable of storing an additional 32 pages. The capacity

12006-459: The machine was faster than the average contemporary system, although slower than "high end" machines like the IBM 7090 by about two to five times. As with any research machine, the DRTE system was used for a number of "household" calculations, as well as the development of a number of simple computer games . These included tic-tac-toe and hangman , as well as a simple music generator that could play

12144-498: The miniature tube version of the " All American Five ". Octodes, such as the 7A8, were rarely used in the United States, but much more common in Europe, particularly in battery operated radios where the lower power consumption was an advantage. To further reduce the cost and complexity of radio equipment, two separate structures (triode and pentode for instance) can be combined in the bulb of a single multisection tube . An early example

12282-438: The modified ITA2 coding scheme to make their job easier. Data was read and written from the papertape punch under program control. The Mark 1 had no system of hardware interrupts ; the program continued after a read or write operation had been initiated until another input/output instruction was encountered, at which point the machine waited for the first to complete. The Mark 1 had no operating system ; its only system software

12420-717: The night of 16/17 June 1949. The algorithm was specified by Max Newman , head of the Mathematics Department at the University of Manchester , and the program was written by Kilburn and Tootill. Alan Turing later wrote an optimised version of the program, dubbed the Mersenne Express. The Manchester Mark 1 continued to do useful mathematical work until 1950, including an investigation of the Riemann hypothesis and calculations in optics . Tootill

12558-431: The number of external pins (leads) often forced the functions to share some of those external connections such as their cathode connections (in addition to the heater connection). The RCA Type 55 is a double diode triode used as a detector, automatic gain control rectifier and audio preamplifier in early AC powered radios. These sets often include the 53 Dual Triode Audio Output. Another early type of multi-section tube,

12696-435: The number of tubes required. Screen grid tubes were marketed by late 1927. However, the useful region of operation of the screen grid tube as an amplifier was limited to plate voltages greater than the screen grid voltage, due to secondary emission from the plate. In any tube, electrons strike the plate with sufficient energy to cause the emission of electrons from its surface. In a triode this secondary emission of electrons

12834-401: The opposite horizon. The movement was controlled by a simple system reading a paper tape. The computer produced tapes so the dish would be slowly rotated as it tracked the satellite, thereby guaranteeing no "dead time". Eventually a library of tapes was built up for any possible pass. Vacuum tube A vacuum tube , electron tube , valve (British usage), or tube (North America)

12972-528: The oscillation valve was developed for the purpose of rectifying radio frequency current as the detector component of radio receiver circuits. While offering no advantage over the electrical sensitivity of crystal detectors , the Fleming valve offered advantage, particularly in shipboard use, over the difficulty of adjustment of the crystal detector and the susceptibility of the crystal detector to being dislodged from adjustment by vibration or bumping. In

13110-402: The paper tape could feed it. The system also offered a crude sort of assembler language support. Using the shift key, characters entered into the system represented mnemonics instead of numerical data, which would then be translated differently. For instance, the letters "AA" would add two floating point numbers, the numbers being stored in the two decimal addresses following. While being read,

13248-523: The paper tape's shift column would signal the BDC decoder to ignore the next codes. The hardware implementation eventually revealed itself as an anti-feature. If one assumed that all the data being read and written was a decimal representation of binary data the system made perfect sense, but if the data was in some other form, more complex assembler language character codes for instance, it ended up simply adding complexity that then had to be turned off. The system

13386-456: The patented ideas developed for the machine, including the Williams tube, in the design of its own 701 and 702 computers. The most significant design legacy of the Manchester Mark 1 was perhaps its incorporation of index registers, the patent for which was taken out in the names of Williams, Kilburn, Tootill, and Newman. Kilburn and Williams concluded that computers would be used more in scientific roles than pure maths, and decided to develop

13524-448: The power supply. Generally this sort of changing load is something that should be avoided wherever possible to reduce noise generated when the power draw increases or decreases. At very low power levels, as in a computer, these pulses of noise can be as powerful as the signals themselves. Although it appears it was never an official recommendation, by the mid-1950s the DRTE decided that the best way to really develop transistor techniques in

13662-399: The power used by the deflection coil. Von Lieben would later make refinements to triode vacuum tubes. Lee de Forest is credited with inventing the triode tube in 1907 while experimenting to improve his original (diode) Audion . By placing an additional electrode between the filament ( cathode ) and plate (anode), he discovered the ability of the resulting device to amplify signals. As

13800-575: The practical use of computers, but it very quickly also became a prototype on which the design of Ferranti 's commercial version could be based. Development ceased at the end of 1949, and the machine was scrapped towards the end of 1950, replaced in February 1951 by a Ferranti Mark 1 , the world's first commercially available general-purpose electronic computer. The computer is especially historically significant because of its pioneering inclusion of index registers , an innovation which made it easier for

13938-448: The present-day C cell , for which the letter denotes its size and shape). The C battery's positive terminal was connected to the cathode of the tubes (or "ground" in most circuits) and whose negative terminal supplied this bias voltage to the grids of the tubes. Later circuits, after tubes were made with heaters isolated from their cathodes, used cathode biasing , avoiding the need for a separate negative power supply. For cathode biasing,

14076-532: The question of thermionic emission and conduction in a vacuum. Consequently, General Electric started producing hard vacuum triodes (which were branded Pliotrons) in 1915. Langmuir patented the hard vacuum triode, but de Forest and AT&T successfully asserted priority and invalidated the patent. Pliotrons were closely followed by the French type ' TM ' and later the English type 'R' which were in widespread use by

14214-477: The reporting in 1949 of what was the first recognisably modern computer provoked a reaction unexpected by its developers; Sir Geoffrey Jefferson , professor of neurosurgery at the University of Manchester, on being asked to deliver the Lister Oration on 9 June 1949 chose "The Mind of Mechanical Man" as his subject. His purpose was to "debunk" the Manchester project. In his address he said: Not until

14352-506: The result. The system did not include an accumulator, the results of all operations being written back to main memory. This was desirable at the time, when computer memories were generally comparable in speed to the processors (today memory is much slower than processors). Florida had previously worked with the team building the Manchester Mark 1 , and following their lead he designed the DRTE machine with 40-bit words. An instruction

14490-438: The same time transistors were still expensive; a tube cost about $ 0.75 while a similar transistor cost about $ 8. This limited the amount of experimentation most companies were able to perform. DRTE was originally formed to improve communications systems , and to this end, they started a research program into using transistors in complex circuits in a new Electronics Lab under the direction of Norman Moody . Between 1950 and 1960,

14628-595: The satellite's orbit, and used this information to calculate the percentage of time that sunlight fell on it. The result proved the system would have more than enough power. While it was designed with a lifetime of only one year, Alouette I eventually ran for ten years before being shut off. The computer was also put into use generating tracking commands for the receiver dish antenna in Ottawa that downloaded data from Alouette. The antenna could not track through "straight up", and had to be rotated 180 degrees to track back down to

14766-436: The signal being looked for. The conventional solution was to wire the read line diagonally back and forth through the plane, so that these smaller signals would cancel out—the positive signal from one would be a negative signal from the next as the wire passed through it in the opposite direction. However this solution also made wiring the core fairly difficult, and considerable amounts of research went into various ways to improve

14904-440: The suppressor grid wired internally to the cathode (e.g. EL84/6BQ5) and those with the suppressor grid wired to a separate pin for user access (e.g. 803, 837). An alternative solution for power applications is the beam tetrode or beam power tube , discussed below. Superheterodyne receivers require a local oscillator and mixer , combined in the function of a single pentagrid converter tube. Various alternatives such as using

15042-444: The teleprinter's keyboard, and output onto its printer. The machine worked internally in binary, but it was able to carry out the necessary decimal to binary and binary to decimal conversions for its input and output respectively. There was no assembly language defined for the Mark 1. Programs had to be written and submitted in binary form, encoded as eight 5-bit characters for each 40-bit word; programmers were encouraged to memorize

15180-458: The triode caused early tube audio amplifiers to exhibit harmonic distortion at low volumes. Plotting plate current as a function of applied grid voltage, it was seen that there was a range of grid voltages for which the transfer characteristics were approximately linear. To use this range, a negative bias voltage had to be applied to the grid to position the DC operating point in the linear region. This

15318-407: The triode. De Forest's original device was made with conventional vacuum technology. The vacuum was not a "hard vacuum" but rather left a very small amount of residual gas. The physics behind the device's operation was also not settled. The residual gas would cause a blue glow (visible ionization) when the plate voltage was high (above about 60 volts). In 1912, de Forest and John Stone Stone brought

15456-437: The tube holding the two index registers, originally known as B-lines, was given the name B. The contents of the registers could be used to modify program instructions, allowing convenient iteration through an array of numbers stored in memory. The Mark 1 also had a fourth tube, (M), to hold the multiplicand and multiplier for a multiplication operation. Of the 20 bits allocated for each program instruction, 10 were used to hold

15594-646: The tube were much greater. In a sense, these were akin to integrated circuits. In the United States, Cleartron briefly produced the "Multivalve" triple triode for use in the Emerson Baby Grand receiver. This Emerson set also has a single tube socket, but because it uses a four-pin base, the additional element connections are made on a "mezzanine" platform at the top of the tube base. By 1940 multisection tubes had become commonplace. There were constraints, however, due to patents and other licensing considerations (see British Valve Association ). Constraints due to

15732-404: The tubes' heaters to be supplied from a common circuit (which can be AC without inducing hum) while allowing the cathodes in different tubes to operate at different voltages. H. J. Round invented the indirectly heated tube around 1913. The filaments require constant and often considerable power, even when amplifying signals at the microwatt level. Power is also dissipated when the electrons from

15870-482: The tubes) without requiring replacement. When triodes were first used in radio transmitters and receivers, it was found that tuned amplification stages had a tendency to oscillate unless their gain was very limited. This was due to the parasitic capacitance between the plate (the amplifier's output) and the control grid (the amplifier's input), known as the Miller capacitance . Eventually the technique of neutralization

16008-406: The vacuum, a process called thermionic emission . This can produce a controllable unidirectional current though the vacuum known as the Edison effect . A second electrode, the anode or plate , will attract those electrons if it is at a more positive voltage. The result is a net flow of electrons from the filament to plate. However, electrons cannot flow in the reverse direction because the plate

16146-436: The value of the most significant bit denotes the sign of a number; positive numbers have a zero in that position and negative numbers a one. Thus the range of numbers that could be held in each 40-bit word was −2 to +2  − 1 (decimal: -549,755,813,888 to +549,755,813,887). The first realistic program to be run on the Mark 1 was a search for Mersenne primes , in early April 1949, which ran error free for nine hours on

16284-421: The voltage applied to the control grid (or simply "grid") was lowered from the cathode's voltage to somewhat more negative voltages, the amount of current from the filament to the plate would be reduced. The negative electrostatic field created by the grid in the vicinity of the cathode would inhibit the passage of emitted electrons and reduce the current to the plate. With the voltage of the grid less than that of

16422-404: Was 1.8 milliseconds, but multiplication was much slower, depending on the size of the operand . The machine's most significant innovation is generally considered to be its incorporation of index registers , commonplace on modern computers. The Baby had included two registers, implemented as Williams tubes: the accumulator (A) and the program counter (C). As A and C had already been assigned,

16560-429: Was a close analogy between the structure of the Mark 1 and the human brain. His article included an interview with Turing, who added: This is only a foretaste of what is to come, and only the shadow of what is going to be. We have to have some experience with the machine before we really know its capabilities. It may take years before we settle down to the new possibilities, but I do not see why it should not enter any of

16698-446: Was a few basic routines for input and output. As in the Baby from which it was developed, and in contrast to the established mathematical convention, the machine's storage was arranged with the least significant digits to the left; thus a one was represented in five bits as "10000", rather than the more conventional "00001". Negative numbers were represented using two's complement , as most computers still do today. In that representation,

16836-402: Was a subconscious choice on his part, a representation of rain seen through a dirty window, reflecting Manchester's "famously dismal" weather. Because the Mark 1 had a 40-bit word length, eight 5-bit teleprinter characters were required to encode each word. Thus for example the binary word: would be represented on paper tape as ZDSLZWRF. The contents of any word in store could also be set via

16974-449: Was also technical consultant to Edison-Swan . One of Marconi's needs was for improvement of the detector , a device that extracts information from a modulated radio frequency. Marconi had developed a magnetic detector , which was less responsive to natural sources of radio frequency interference than the coherer , but the magnetic detector only provided an audio frequency signal to a telephone receiver. A reliable detector that could drive

17112-425: Was broken down into four 10-bit parts, the instruction and three 10-bit addresses. This allowed a total main memory size of 2^10 = 1024 40-bit words, or 40 kB in modern terminology. Integers used 39 bits and one bit for a sign, while floating point numbers had an 8-bit exponent with one bit for the sign and a 32-bit mantissa with one bit for the sign. Florida felt that the three-address instruction format, including

17250-405: Was called the idle condition, and the plate current at this point the "idle current". The controlling voltage was superimposed onto the bias voltage, resulting in a linear variation of plate current in response to positive and negative variation of the input voltage around that point. This concept is called grid bias . Many early radio sets had a third battery called the "C battery" (unrelated to

17388-617: Was developed whereby the RF transformer connected to the plate (anode) would include an additional winding in the opposite phase. This winding would be connected back to the grid through a small capacitor, and when properly adjusted would cancel the Miller capacitance. This technique was employed and led to the success of the Neutrodyne radio during the 1920s. However, neutralization required careful adjustment and proved unsatisfactory when used over

17526-417: Was entirely transistor-based, and later patented. Another improvement introduced in their core design involved the handling of the read wire. Reading a location in core works by powering the address in question, as if you wanted to write a "1" to that location. If the core was already holding a "1" nothing will happen. However, if the core was holding a "0", the power will cause the core to change polarity to

17664-410: Was eventually removed when assembler programming became common. It also seriously limited the sorts of devices that could be hooked up, due to the careful tuning of the interface speed. As soon as the prototype math unit was completed in 1957, a new unit that operated on an entire word in parallel was started. This new unit was ready around the same time as the "full version" of the machine (1960–61) and

17802-495: Was implemented inline with the I/O systems. This allowed the paper tape to be punched in decimal codes which would be converted invisibly into binary and stored in memory while being read. The reverse was also true, allowing the machine to print the contents of memory directly to tape again. The system was tuned so that the machine could read or write data essentially for free; that is, the system could read and store data exactly as fast as

17940-432: Was increased in the Final Specification version to eight pages of main store on four Williams tubes and 128 magnetic drum pages of backing store. The 12-inch (300 mm) diameter drum, initially known as a magnetic wheel, contained a series of parallel magnetic tracks around its surface, each with its own read/write head. Each track held 2,560 bits, corresponding to two pages (2×32×40 bits). One revolution of

18078-407: Was later retrofitted into the design. This improved speeds by about ten times, for instance, a floating-point add improved from 300 μs to only 40, multiplication from 2200 to 180 μs, and a square root from 5300 to 510 microseconds. Integer math was likewise improved by about the same factor, although "complex" arithmetic like multiplication remained in code as opposed to hardware. With the new math unit

18216-617: Was no separate program stored in memory, as in a modern computer. It could take several days to reprogram ENIAC , for instance. Stored-program computers were also being developed by other researchers, notably the National Physical Laboratory 's Pilot ACE , Cambridge University 's EDSAC , and the US Army 's EDVAC . The Baby and the Mark 1 differed primarily in their use of Williams tubes as memory devices, instead of mercury delay lines . From about August 1948,

18354-585: Was one of the earliest stored-program computers , developed at the Victoria University of Manchester , England from the Manchester Baby (operational in June 1948). Work began in August 1948, and the first version was operational by April 1949; a program written to search for Mersenne primes ran error-free for nine hours on the night of 16/17 June 1949. The machine's successful operation

18492-411: Was recorded onto the drum using a phase modulation technique still known today as Manchester coding . The machine's instruction set was increased from the 7 of the Baby to 26 initially, including multiplication done in hardware. This increased to 30 instructions in the Final Specification version. Ten bits of each word were allocated to hold the instruction code . The standard instruction time

18630-578: Was selected; it has been suggested this was due to it being Prime Minister's John Diefenbaker home riding. The new site was opened in June 1959, known as the Prince Albert Radar Laboratory , or PARL . In order to quickly record data during test runs, the DRTE built a custom system known as DAR , the Digital Analyzer and Recorder . DAR was a fairly high-priority project, and some of the manpower originally working on

18768-406: Was temporarily transferred from the University of Manchester to Ferranti in August 1949, to continue work on the Ferranti Mark 1's design, and spent four months working with the company. The Manchester Mark 1 was dismantled and scrapped in August 1950, replaced a few months later by the first Ferranti Mark 1, the world's first commercially available general-purpose computer. Between 1946 and 1949,

18906-401: Was usually connected to the cathode and its negative voltage relative to the anode repelled secondary electrons so that they would be collected by the anode instead of the screen grid. The term pentode means the tube has five electrodes. The pentode was invented in 1926 by Bernard D. H. Tellegen and became generally favored over the simple tetrode. Pentodes are made in two classes: those with

19044-449: Was widely reported in the British press, which used the phrase "electronic brain" in describing it to their readers. That description provoked a reaction from the head of the University of Manchester's Department of Neurosurgery, the start of a long-running debate as to whether an electronic computer could ever be truly creative . The Mark 1 was to provide a computing resource within the university, to allow researchers to gain experience in

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