omniomni/omni-engineering huggingface dataset:
FDM. FDM may refer to:

 Fascial Distortion Model, a model of medicine developed by American physician Stephen Typaldos
 Fat in dry matter, a measurement of fat content in the dry matter of cheeses
 fdm (software), a mail delivery agent and email filtering software
 FDM Group, a British multinational information technology consulting company
 Federation of Danish Motorists, an automobile association
 Finite difference method, a class of numerical techniques for solving differential equations
 Flight operations quality assurance (also flight data monitoring), a method of capturing, analyzing and/or visualizing the data generated by an aircraft
 Frequency-division multiplexing, a technique by which the total bandwidth available in a communication medium is divided
 Fused filament fabrication (also fused deposition modeling), a 3D printing process
Any key. In computing, "Press any key to continue" (or a similar text) was a historically used prompt to the user when it was necessary to pause processing. The system would resume after the user pressed any keyboard button.

History

Early computers were typically operated using mechanical teleprinters, which provided a continuous printed record of their output. However, during the 1970s, these became obsolete and were replaced with visual display units, and text was lost once it scrolled off the top of the screen. To compensate, programs typically paused operation after displaying one screen of data, so that the user could observe the results and then press a key to move to the next screen.

A similar pause was also required when some physical action was required from the user, such as inserting a floppy disk or loading a printer with paper.

These prompts were commonplace on text-based operating systems prior to the development of graphical user interfaces, which typically included scrollbars to enable the user to view more than one screen/window of data. They are therefore no longer required as a means of paginating output, but the graphical equivalent (such as a modal dialog box containing the text "Click OK to continue") is still used for hardware interactions.

The prompt ("any key") is not strictly accurate, in that one is required to press a key which generates some sort of character. For the vast majority of computer systems, pressing modifier keys or lock keys would not cause processing to resume, as they do not produce an actual character that the program could detect.

Some Samsung remote controls for DVD players, as is the case of DVD-R130, have included an "anykey" to their interface. It is used to view the status of the DVD being watched.

Cultural significance

A 1982 Apple Computer manual for developers warned:

There are reports from as early as 1988 that some users have searched for such a key labelled "any", and called technical support when they have been unable to find it. The computer company Compaq even edited their FAQ to explain that the "any" key does not exist, and at one point considered replacing the command "Press any key" with "Press return key".

The concept of the "any key" has become a popular piece of computer-related humor, and was used as a gag on The Simpsons, in the seventh-season episode "King-Size Homer", where Homer Simpson searches the keyboard looking for "the any key".

Plastic "ANY keys" with adhesive backings are available as novelty gifts.

References

Computer keys
Computer humour
Latin hypercube sampling. Latin hypercube sampling (LHS) is a statistical method for generating a near-random sample of parameter values from a multidimensional distribution. The sampling method is often used to construct computer experiments or for Monte Carlo integration.

LHS was described by Michael McKay of Los Alamos National Laboratory in 1979. An equivalent technique was independently proposed by Vilnis Eglājs in 1977.   It was further elaborated by Ronald L. Iman and coauthors in 1981. Detailed computer codes and manuals were later published.

In the context of statistical sampling, a square grid containing sample positions is a Latin square if (and only if) there is only one sample in each row and each column. A Latin hypercube is the generalisation of this concept to an arbitrary number of dimensions, whereby each sample is the only one in each axis-aligned hyperplane containing it.

When sampling a function of  variables, the range of each variable is divided into  equally probable intervals.  sample points are then placed to satisfy the Latin hypercube requirements; this forces the number of divisions, , to be equal for each variable. This sampling scheme does not require more samples for more dimensions (variables); this independence is one of the main advantages of this sampling scheme. Another advantage is that random samples can be taken one at a time, remembering which samples were taken so far.

In two dimensions the difference between random sampling, Latin hypercube sampling, and orthogonal sampling can be explained as follows:
In random sampling new sample points are generated without taking into account the previously generated sample points. One does not necessarily need to know beforehand how many sample points are needed.
In Latin hypercube sampling one must first decide how many sample points to use and for each sample point remember in which row and column the sample point was taken. Such configuration is similar to having N rooks on a chess board without threatening each other.
In orthogonal sampling, the sample space is partitioned into equally probable subspaces. All sample points are then chosen simultaneously making sure that the total set of sample points is a Latin hypercube sample and that each subspace is sampled with the same density.

Thus, orthogonal sampling ensures that the set of random numbers is a very good representative of the real variability, LHS ensures that the set of random numbers is representative of the real variability whereas traditional random sampling (sometimes called brute force) is just a set of random numbers without any guarantees.

References

Further reading

Sampling techniques
Latin squares
Design of experiments
1979 introductions
Bridge circuit. A bridge circuit is a topology of electrical circuitry in which two circuit branches (usually in parallel with each other) are "bridged" by a third branch connected between the first two branches at some intermediate point along them.  The bridge was originally developed for laboratory measurement purposes and one of the intermediate bridging points is often adjustable when so used.  Bridge circuits now find many applications, both linear and non-linear, including in instrumentation, filtering and power conversion.

The best-known bridge circuit, the Wheatstone bridge, was invented by Samuel Hunter Christie and popularized by Charles Wheatstone, and is used for measuring resistance. It is constructed from four resistors, two of known values R1 and R3 (see diagram), one whose resistance is to be determined Rx, and one which is variable and calibrated R2.  Two opposite vertices are connected to a source of electric current, such as a battery, and a galvanometer is connected across the other two vertices. The variable resistor is adjusted until the galvanometer reads zero.  It is then known that the ratio between the variable resistor and its neighbour R1 is equal to the ratio between the unknown resistor and its neighbour R3, which enables the value of the unknown resistor to be calculated.

The Wheatstone bridge has also been generalised to measure impedance in AC circuits, and to measure resistance, inductance, capacitance, and dissipation factor separately. Variants are known as the Wien bridge, Maxwell bridge, and Heaviside bridge (used to measure the effect of mutual inductance).  All are based on the same principle, which is to compare the output of two potential dividers sharing a common source.

In power supply design, a bridge circuit or bridge rectifier is an arrangement of diodes or similar devices used to rectify an electric current, i.e. to convert it from an unknown or alternating polarity to a direct current of known polarity.

In some motor controllers, an H-bridge is used to control the direction the motor turns.

Bridge current equation

From the figure to the right, the bridge current is represented as I5

Per Thévenin's theorem, finding the Thévenin equivalent circuit which is connected to the bridge load R5 and using the arbitrary current flow I5, we have:

Thevenin Source (Vth) is given by the formula:

and the Thevenin resistance (Rth):

Therefore, the current flow (I5) through the bridge is given by Ohm's law:

and the voltage (V5) across the load (R5) is given by the voltage divider formula:

See also 
 Phantom circuit - a use of balanced bridge circuits in telephony
 Lattice filter -  an application of bridge topology to all-pass filters

Gallery

References

External links
Jim Williams, "Bridge circuits: Marrying gain and balance", Linear Technology Application Note 43, June 1990.
Bridge circuits - Chapter 8 from an online book.
ELF II. The Netronics ELF II was an early microcomputer trainer kit featuring the RCA 1802 microprocessor, 256 bytes of RAM, DMA-based bitmap graphics, hexadecimal keypad, two-digit hexadecimal LED display, a single "Q" LED, and 5 expansion slots. The system was developed and sold by Netronics Research and Development Limited in New Milford, CT, USA.

Hardware 
Available hardware accessories included:
 The "Giant Board" (ROM monitor, serial and parallel I/O, Cassette interface)
 4KB and 16KB (static) RAM boards
 Low-resolution color graphics board
 "Full BASIC" board with BASIC preloaded in ROM chips
 EPROM burner board
 External power supply
 Attractive, heavy-duty metal cases for the CPU and power supply

Software
Available software included:
 Tiny BASIC (integer BASIC interpreter)
 Text Editor
 Full BASIC (floating point BASIC interpreter using Reverse Polish Notation)

Notable Features
 Unlike similar "bare circuit card" trainer/experimenter computers of the day, the ELF II could be easily expanded thanks to its built-in bus.
 Memory mapped TV graphics was provided in the base kit by the CDP1861 "Pixie-Graphics" chip. Pixels were large. With unexpanded 256 byte memory, the interrupt routine needed to service the chip showed on the screen.
 The "Full BASIC" ROM card provided an RPN calculator chip as a simple and low-cost math coprocessor.  As a result, floating point operations were an order of magnitude faster than what was possible in software. However, the BASIC syntax for math was non-standard as it used postfix RPN (see code example below). Historically, this was also the heyday of Hewlett-Packard calculators, so it was a fair bet that any technically-minded person willing to assemble a computer either already knew RPN or could easily learn it and adapt.10 REM This program will print the number 30
20 A=10,B=20
30 C=A#B+
40 PRINT C
50 END In the code above, the "#" symbol is equivalent to the "Enter" key on a RPN calculator.

Netronics Video Terminal
Netronics also offered:
 An ASCII keyboard kit
 Heavy-duty metal keyboard case
 Video terminal card kit (monochrome text, 16 lines by 64 characters, upper & lower case)
The keyboard could be used alone to generate ASCII parallel codes.  The video terminal card fits underneath the keyboard in the optional case to form a stand-alone video terminal sending and receiving serial ASCII. Either configuration could be interfaced to the ELF II through the Giant Board.  The terminal kits were also marketed independently of the ELF II.

The Name 
The ELF part of the name came from an earlier machine called the "COSMAC ELF", published as a construction project in Popular Electronics magazine. Improvements on its predecessor included an etched PCB, a hexadecimal keypad instead of toggle switches for program entry, the RCA CDP1861 Pixie-graphics chip, and the 5 slot 86-line bus for expansion cards.

See also
COSMAC ELF
RCA COSMAC VIP
Quest SuperELF
RCA 1802 microprocessor
Early Microcomputers
Competing 6502 microprocessor based trainers KIM-1 and Rockwell AIM-65
8080 Based machines: MITS Altair 8800 and IMSAI 8080
RCA Studio II

References

External links 
 

Early microcomputers
Texas Instruments Graphics Architecture. Texas Instruments Graphics Architecture (TIGA) is a graphics interface standard created by Texas Instruments that defined the software interface to graphics processors. Using this standard, any software written for TIGA should work correctly on a TIGA-compliant graphics interface card.

The TIGA standard is independent of resolution and color depth which provides a certain degree of future proofing. This standard was designed for high-end graphics. However, TIGA was not widely adopted. Instead, VESA and Super VGA became the de facto standard for PC graphics devices after the VGA. Texas Instrument's TMS34010 and TMS34020 Graphics System Processors (GSP) were the original TIGA-compliant graphics processors.

Clone Hardware
The primary manufacturers of mainstream TIGA cards for the PC clone market included Number Nine Visual Technology and Hercules. Number Nine Visual Technology graphics cards using Texas Instruments' TIGA co-processors were made from about 1986 to 1992, including the Pepper and GX series. Hercules manufactured cards such as the Graphics Station and Chrome lines which were marketed primarily toward users of Microsoft Windows.

Desktop Computing AGA 1024 card was capable of emulating TIGA standards, besides IBM 8514.

In the early 1990s, Texas Instruments France (which had marketing control for TIGA architecture and GSP chipsets in Europe) experimented with manufacturing and selling its own range of consumer oriented video cards based on TIGA and aimed at speeding up the user experience of Windows. These products were named TIGA Diamond (34020 based) and TIGA Star (34010 based), and provided a platform for selling TI DRAM and video palette chips as well as the GSP chips themselves.

Impact
Despite the superiority of the technology in comparison to typical Super VGA cards of the era, the relatively high cost and emerging local bus graphics standards meant that IT distributors and PC manufacturers could not see a niche for these products at consumer level.

The (limited) success of the graphics cards paved the way for products based upon various derivatives and clones of IBM's 8514 architecture. Part of the effort to make graphics accelerators useful required TI to convince Microsoft that the internal interfaces to its Windows Operating System had to be adaptable instead of hard-coded. Indeed, all versions of Windows prior to Windows 3.0 were "hard-coded" to specific graphics hardware.

See also 
 TMS34010
 Number Nine Visual Technology TIGA cards
 VESA
 Super VGA
 IBM 8514

References

External links
TMS340 Interface User's Guide spvu015c
TMS340 FAMILY GRAPHICS LIBRARY USER'S GUIDE spvu027

Texas Instruments hardware
Graphics cards
Stub Series Terminated Logic. Stub Series Terminated Logic (SSTL)  is a group of electrical standards for driving transmission lines commonly used with DRAM based DDR memory IC's and memory modules. SSTL is primarily designed for driving the DDR (double-data-rate) SDRAM modules used in computer memory; however, it is also used in other applications, notably some PCI Express PHYs and other high-speed devices.

Four voltage levels for SSTL are defined:
SSTL_3, 3.3 V, defined in EIA/JESD8-8 1996
SSTL_2, 2.5 V, defined in EIA/JESD8-9B 2002 used in DDR among other things.
SSTL_18, 1.8 V, defined in EIA/JESD8-15A, used in DDR2 among other things.
SSTL_15, 1.5 V, used in DDR3 among other things.

SSTL_3 uses a reference of 0.45 * VDDQ (1.5 V).  SSTL_2 and SSTL_18 reference a voltage that is exactly VDDQ / 2 (1.25 V and 0.9 V respectively).

SSTL_3 and SSTL_2 support two termination classes (50 ohm or 25 ohm load). SSTL_18 only supports one (25 ohm load).

See also
High-Speed Transceiver Logic - HSTL

References

External links 
JEDEC homepage links; require (free) login:
 JEDEC SSTL_2 Standard (JESD8-9B)
 JEDEC SSTL_18 Standard (JESD8-15A)

Computer memory
JEDEC standards
High-speed transceiver logic. High-speed transceiver logic or HSTL is a technology-independent standard for signaling between integrated circuits.  The nominal signaling range is 0 V to 1.5 V, though variations are allowed, and signals may be single-ended or differential. It is designed for operation beyond 180 MHz.

The following classes are defined by standard EIA/JESD8-6 from EIA/JEDEC:
Class I (unterminated, or symmetrically parallel terminated)
Class II (series terminated)
Class III (asymmetrically parallel terminated)
Class IV (asymmetrically double parallel terminated)

Note that Symmetric parallel termination means that the termination resistor at the load is connected to half the output buffer's supply voltage. Double parallel termination means that parallel termination resistors are fitted at both ends of the transmission line.

See also
Stub Series Terminated Logic - SSTL

References

Digital electronics
JEDEC standards
Egide Walschaerts. Egide Walschaerts (21 January 1820 – 18 February 1901) was a Belgian mechanical engineer, best known as the inventor of the Walschaerts valve gear used in steam locomotives. He was born in Mechelen, Belgium. In 1838 he was recognised as an excellent modeller, presenting his work at a local exhibition in Mechelen. Minister Rogier, who opened the exhibition, was so impressed that he arranged a place for Walschaerts at Liège University.

Career
In 1842 he joined the Belgian State Railways and two years later had reached the rank of foreman.  He was made chief superintendent of the works shortly after but mysteriously, for such a meteoric early career, never rose any higher. He held this position for the rest of his life, first at Mechelen and then at Brussels South.

Walschaerts valve gear

Whilst at Mechelen in 1844 he developed a new type of valve gear (a mechanism that allows for adjustment of the travel of the valves that distribute the steam to the cylinders and enables a steam locomotive to be put into reverse and to economise steam). He was not permitted by the company to patent the device himself as he was deemed of too lowly a rank. An engineer colleague and friend, M. Fisher, applied for the patent on his behalf but never claimed any contribution to it. Walschaerts's name on the documents erroneously omitted the final 's' causing confusion over its correct spelling over the succeeding years.  A locomotive built at the Tubize workshops fitted with the Walschaerts valve gear was awarded a gold medal at the 1873 Universal Exhibition in Vienna. This valve gear came to be used in the majority of steam locomotives, and became almost universal throughout the 20th Century.

Other innovations
According to Payen, in 1874 Walschaerts developed a particularly successful version of the Corliss stationary engine that won a gold medal at the 1878 Exposition Universelle in Paris.

Commemoration
Both of the municipalities in which he worked have named streets after him: Mechelen and St Gillis/St-Gilles in Brussels (Egide is a form of the name Giles).

References

1820 births
1901 deaths
19th-century Belgian engineers
Belgian mechanical engineers
Locomotive builders and designers
People from Mechelen
RH. RH, Rh, rH, or rh may refer to:

Companies
 Red Hat, an American software company
 Republic Express Airlines (IATA designator), a cargo airline in Indonesia
 RH (company), an American furniture chain formerly known as Restoration Hardware

Science and technology
 Relative humidity, the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature
 Releasing hormone
 Reproductive health
 Rh blood group system (Rhesus factor), a classification to describe blood types in humans
 Rhodium, symbol Rh, a chemical element
 RH, the Rydberg constant for hydrogen
 Riemann hypothesis, an important unsolved problem in mathematics
 Adobe RoboHelp, an Adobe software

Places
 RH postcode area, in the UK
 , an official name of Croatia in Croatian

Other uses
 Rh (digraph)
 The Right Honourable, an honorific preceding a name in the UK
 Radical honesty, the practice of always being completely honest and refraining from telling even white lies
 DZRH News Television, a news channel in the Philippines previously known as RHTV.

See also
 DZRH, a Philippine radio station
 Royal Hospital (disambiguation)
Church–Turing–Deutsch principle. In computer science and quantum physics, the Church–Turing–Deutsch principle (CTD principle) is a stronger, physical form of the Church–Turing thesis formulated by David Deutsch in 1985. The principle states that a universal computing device can simulate every physical process.

History
The principle was stated by Deutsch in 1985 with respect to finitary machines and processes. He observed that classical physics, which makes use of the concept of real numbers, cannot be simulated by a Turing machine, which can only represent computable reals. Deutsch proposed that quantum computers may actually obey the CTD principle, assuming that the laws of quantum physics can completely describe every physical process.

An earlier version of this thesis for classical computers was stated by Alan Turing's friend and student Robin Gandy in 1980.

A similar thesis was stated by Michael Freedman in an early review of topological quantum computing with Alexei Kitaev, Michael J. Larsen, and Zhenghan Wang, known as the Freedman-Church-Turing thesis:

This thesis differs from the Church-Turing-Deutsch thesis insofar as it is a statement about computational complexity, and not computability.

See also
 Bekenstein bound
 Digital physics
 Holographic principle 
 Quantum complexity theory
 Laplace's demon

Notes

References

Further reading

 Christopher G. Timpson Quantum Computers: the Church-Turing Hypothesis Versus the Turing Principle in Christof Teuscher, Douglas Hofstadter (eds.) Alan Turing: life and legacy of a great thinker, Springer, 2004, , pp. 213–240

External links

Alan Turing
Principles
Computability theory
Theory of computation