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Counter (digital)

In digital logic and computing, a counter is a device which stores the number of times a particular event or process has occurred in relationship to a clock. The most common type is a sequential digital logic circuit with an input line called the clock and multiple output lines; the values on the output lines represent a number in the BCD number system. Each pulse decrements the number in the counter. A counter circuit is constructed of a number of flip-flops connected in cascade. Counters are a widely used component in digital circuits, are manufactured as separate integrated circuits and incorporated as parts of larger integrated circuits. In electronics, counters can be implemented quite using register-type circuits such as the flip-flop, a wide variety of classified into: Asynchronous counter – changing state bits are used as clocks to subsequent state flip-flops Synchronous counter – all state bits change under control of a single clock Decade counter – counts through ten states per stage Up/down counter – counts both up and down, under command of a control input Ring counter – formed by a shift register with feedback connection in a ring Johnson counter – a twisted ring counter Cascaded counter Modulus counter.

Each is useful for different applications. Counter circuits are digital in nature, count in natural binary. Many types of counter circuits are available as digital building blocks, for example a number of chips in the 4000 and 4500 series implement different counters. There are advantages to using a counting sequence other than the natural binary sequence—such as the binary coded decimal counter, a linear-feedback shift register counter, or a Gray-code counter. Counters are useful for digital clocks and timers, in oven timers, VCR clocks, etc. An asynchronous counter is a single d-type flip-flop, with its J input fed from its own inverted output; this circuit can store one bit, hence can count from zero to one before it overflows. This counter will increment once for every clock cycle and takes two clock cycles to overflow, so every cycle it will alternate between a transition from 0 to 1 and a transition from 1 to 0. Notice that this creates a new clock with a 50% duty cycle at half the frequency of the input clock.

If this output is used as the clock signal for a arranged D flip-flop, one will get another 1 bit counter that counts half as fast. Putting them together yields a two-bit counter: You can continue to add additional flip-flops, always inverting the output to its own input, using the output from the previous flip-flop as the clock signal; the result is called a ripple counter, which can count to 2n - 1 where n is the number of bits in the counter. Ripple counters suffer from unstable outputs as the overflows "ripple" from stage to stage, but they do find frequent application as dividers for clock signals, where the instantaneous count is unimportant, but the division ratio overall is; the use of flip-flop outputs as clocks leads to timing skew between the count data bits, making this ripple technique incompatible with normal synchronous circuit design styles. In synchronous counters, the clock inputs of all the flip-flops are connected together and are triggered by the input pulses. Thus, all the flip-flops change state simultaneously.

The circuit below is a 4-bit synchronous counter. The J and K inputs of FF0 are connected to HIGH. FF1 has its J and K inputs connected to the output of FF0, the J and K inputs of FF2 are connected to the output of an AND gate, fed by the outputs of FF0 and FF1. A simple way of implementing the logic for each bit of an ascending counter is for each bit to toggle when all of the less significant bits are at a logic high state. For example, bit 1 toggles. Synchronous counters can be implemented with hardware finite-state machines, which are more complex but allow for smoother, more stable transitions. A decade counter is one, rather than binary. A decade counter may have other binary encodings. "A decade counter is a binary counter, designed to count to 1010. An ordinary four-stage counter can be modified to a decade counter by adding a NAND gate as in the schematic to the right. Notice that FF2 and FF4 provide the inputs to the NAND gate; the NAND gate outputs are connected to the CLR input of each of the FFs."

A decade counter is one, rather than binary. It counts from 0 to 9 and resets to zero; the counter output can be set to zero by pulsing the reset line low. The count increments on each clock pulse until it reaches 1001; when it increments to 1010 both inputs of the NAND gate go high. The result is that the NAND output goes low, resets the counter to zero. D going low can be a CARRY OUT signal. A ring counter is a circular shift register, initiated such that only one of its flip-flops is the state one while others are in their zero states. A ring counter is a shift register with the output of the last one connected to the i

David A. Huffman

David Albert Huffman was an American pioneer in computer science, known for his Huffman coding. He was one of the pioneers in the field of mathematical origami. David Huffman died ten months after being diagnosed with cancer. Huffman earned his bachelor's degree in electrical engineering from Ohio State University in 1944 served two years as an officer in the United States Navy, he returned to Ohio State to earn his master's degree in electrical engineering in 1949. In 1953, he earned his Doctor of Science in electrical engineering at the Massachusetts Institute of Technology, with the thesis The Synthesis of Sequential Switching Circuits, advised by Samuel H. Caldwell. Huffman joined the faculty at MIT in 1953. In 1967, he joined the faculty of University of California, Santa Cruz and helped found its Computer Science Department, where he served as chair from 1970 to 1973, he retired in 1994. 1955: The Louis E. Levy Medal from the Franklin Institute for his doctoral thesis on sequential switching circuits.

1973: The W. Wallace McDowell Award from the IEEE Computer Society. 1981: Charter recipient of the Computer Pioneer Award from the IEEE Computer Society. 1998: A Golden Jubilee Award for Technological Innovation from the IEEE Information Theory Society, for "the invention of the Huffman minimum-length lossless data-compression code". 1999: The IEEE Richard W. Hamming Medal. Huffman, Ken. "My Uncle". Huffman Coding. Retrieved June 17, 2011. Haeberli, Paul. "Geometric Paper Folding: Dr. David Huffman". GRAFICA Obscura. Retrieved June 17, 2011. Wertheim, Margaret. "Cones, Shells, Towers: He Made Paper Jump to Life". New York Times. Retrieved June 17, 2011

Australian Formula 1

Australian Formula 1 was a motor sport category for open-wheeler racing cars, current in Australia from 1970 to 1983. AF1 was introduced by the Confederation of Australian Motor Sport in 1970 restricting cars to unsupercharged engines of no greater than 2.5-litre capacity, running on commercial fuel. AF1 was a new name for the Australian National Formula, Australia’s premier racing category from 1964 to 1969. Effective 23 February 1971, AF1 was changed to a two-part formula catering for racing cars fitted with 5.0-litre production based pushrod V8 engines and those fitted with less restricted unsupercharged engines of eight cylinders or less and up to 2000 cc in capacity. The smaller engine option was discontinued after 1976; the main engines used were Chevrolet and Repco-Holden V8's, though a Ford V8 was seen in action without success. In March 1979 Formula Pacific cars became eligible for Australian Formula 1 alongside the existing 5.0-litre cars and 1980 saw the addition of 3.0-litre FIA Formula One cars to the mix.

For 1982, Australian Formula 1 was restricted to Formula Pacific cars only. In 1983 CAMS adopted Formula Mondial as the new Australian Formula 1 but allowed cars complying with Formula Pacific to compete alongside the new cars for that year. For 1984 CAMS changed the category name from “Australian Formula 1” to “Formula Mondial”; the Australian Drivers' Championship was open to drivers of AF1 cars throughout the life of the formula, i.e. from 1970 to 1983. During those years the term Australian Formula 1 Championship was used in lieu of Australian Drivers Championship however the latter is used by the Confederation of Australian Motor Sport in its official records of the championship; the Australian Grand Prix was contested by AF1 cars during the years 1970 to 1983 inclusive, although the 1970 event permitted Formula 5000 cars and the 1981 race was restricted to cars complying with the Formula Pacific section of AF1. CAMS Manuals of Motor Sport, 1964 through 1984

Coding House

Coding House was a coding bootcamp in Silicon Valley, California. The 14-week-long bootcamp taught other technologies. Founded in 2014 by Nicholas James, it was ordered shut down in November 2016 by the regulatory agency California Bureau for Private Postsecondary Education for violating California law many times. BPPE denied Coding House's licensing application three times and found that Coding House had engaged in false advertising. Coding House was founded in 2014 by Nicholas James. Based in Silicon Valley, the bootcamp operated in two places in Fremont, California and in a place in Pleasanton, California. Coding House held 14-week-long bootcamps in which students would live on campus while learning the curriculum; the bootcamp cost 18 % of the graduate's initial year of salary. It focused on teaching students other technologies. In 2014, online lending marketplace Upstart offered loans for students attending bootcamps like Coding House. In September 2016, Coding House mandated that students sign non-disparagement contracts disallowing them from either publicly or criticizing the school.

If Coding House determined that students had originated damaging information about it, Coding House vowed to take action against the students. The California Bureau for Private Postsecondary Education, tasked with regulating California coding schools, declined to add Coding House to its list of approved programs, it first warned Coding House in a cease and desist in January 2014 that it was unlicensed to operate as a coding bootcamp. BPPE rejected Coding House's applications in November 2015, in June 2016, on November 4, 2016. On November 7, 2016, the BPPE levied a $50,000 fine on Coding House founder Nicholas James and mandated that James close the school. BPPE further decreed that Coding House reimburse every single student who had enrolled in the school. Coding House filed an appeal but discontinued classes in the meantime. BPPE shut the school down because it found Coding House had committed many contraventions of California law. BPPE determined. Coding House said on its website that 95% of its alumni received employment by two months after completing the curriculum and that their average starting salary was $91,000.

However, BPPE found that just 57 of Coding House's 70 graduates had provided details about their jobs and salaries. The school had 21 companies in a ``. However, BPPE determined from an analysis of Coding House's records that just two alumni had been hired by either of the 21 companies. BPPE ruled that Coding House contravened home-occupation permit rules by functioning in residential neighborhoods. BPPE additionally found that at Coding House a male student had sexually assaulted a female student while people were drinking alcohol. "Coding House Institute. Disciplinary Actions – California Bureau for Private Postsecondary Education". California Bureau for Private Postsecondary Education. Retrieved 2016-12-29. Official website

Stone Mountain Scenic Railroad

The Stone Mountain Scenic Railroad is a standard gauge railroad that circles the perimeter of Stone Mountain Park in a loop, provides views of the mountain en route. The railroad utilizes what was an industrial spur built in 1869 by the Stone Mountain Granite Company to serve quarries at the foot of the Stone Mountain, with a connection to the Georgia Railroad's main line in Stone Mountain Village; the railroad started an excursion service to the mountain. The spur was abandoned, leaving the right of way in place. In 1960, Stone Mountain Scenic Railroad, Inc. was formed to construct a tourist railroad encircling the mountain, operating it under lease from the Stone Mountain Memorial Association. Between 1961 and 1963, two miles of former quarry trackage were rebuilt, followed by construction of additional new trackage to complete the road around the perimeter of the mountain; the mileage of the circuit around the mountain is advertised as being 5 miles long, the actual mileage is 3.88 miles.

The Stone Mountain Memorial Association assumed full operation of the railroad in 1981. As the steam locomotives came in need of major repairs, the road opted to withdraw them and operate diesels. In 1987, the spur connecting the mountain trackage to the CSX main line was restored, the railroad hosted several visiting trains, including Savannah and Atlanta Railway steam locomotive number 750. With the connection, the railroad became subject to FRA regulations, in which case the road, just as the railroad to which it is connected, was required to maintain its track and rolling stock to a certain degree of good repair to be permitted to operate. In January 1998, the Memorial Association leased operations of the railroad and the other attractions within the park to Herschend Family Entertainment, operators of the Silver Dollar City theme park in Branson and the Dollywood theme park in Pigeon Forge, Tennessee. In 2004, the trackage connecting the railroad to the main line was dismantled and the spur truncated to just before the bridge spanning Robert E. Lee Boulevard within the park's premises.

The trackage and decking were removed, though the bridge's girders remain, the right of way to the west of the bridge was converted to a pedestrian trail, while the railroad continues to use the remaining track to reverse the train's direction. Contrary to the perceptions of the railfan community regarding the disconnection, the railroad remains subject to the FRA's jurisdiction and continues to maintain the equipment and trackage accordingly. In 2011, major upgrades of the track, passenger cars, diesel locomotives were performed; the diesel locomotives received other upgrades, as well as a new paint scheme. The steam locomotives received some cosmetic restoration at this time as well; the railroad had de-accessioned its last remaining steam locomotives in early 2013, owns and operates diesels exclusively. Stone Mountain had three steam locomotives, the "General II," "Texas II," and "Yonah II." The SMRR named the engines after the famous engines of The Great Locomotive Chase, were given nineteenth century style smokestacks and headlights.

Despite these modifications, the engines, having been built between 1919 and 1927, still have noticeably modern appearances, with larger proportions than their ancestors and have more advanced cylinders, valve gear, other modern applications. While steam engines ceased running in the 1980s, they continued to "pull" trains for some time. In these instances, one of the steam engines was coupled in front of a diesel which, while disguised as a baggage car or auxiliary tender, would push the engine; the diesel's controls were placed in the cab of the engine and air piped from the diesel's main reservoir to allow the steam engine's whistle to sound. Aside from the whistle, the steam locomotive remained inactive, with the diesel being the train's sole motive power. In the late 1980s and early 90s, the railroad supplemented its GP7 and GP9 diesels with ones inherited from the dissolved New Georgia Railway, which have pulled trains since. At that time, the steam engines would only be pushed on special occasions, no attempt was made to disguise the diesel behind it.

The practice of pushing the steam engines ended in 2002, they remained within the yard until being donated to other tourist railroads or museums, the first leaving the railroad in 2008, followed by the remaining two in 2013. The Stone Mountain Railroad has the following locomotives: 6143 and 6147 - Two FP7A diesel locomotives built by EMD in 1950 for Southern Railway's Chicago, New Orleans, Texas Pacific subsidiary. SOU successor Norfolk Southern sold these diesels to the New Georgia Railway, were turned over to Stone Mountain upon the New Georgia's demise. One of these locomotives can be found pulling the train on a daily basis. In 2011, both locomotives underwent a major rebuild; when finished the two will have new diesel prime movers, new main and auxiliary generators, new air compressors, a full 26L air brake system installed, rebuilt trucks with D87 traction motors, rewired with Dash-2 control mechanisms, air conditioned cabs, upgraded cab layout, repainted in a Central of Georgia style paint scheme, power generators installed in the rear of the locomotives to supply power for the passenger cars.

This upgrades the 1500 horsepower locomotives to 2000 horsepower and extends their life by at least 15 to 20 years. #5896 - A former Chesapeake and Ohio Railroad GP7 diesel built by EMD in 1953. This engine is occasi

Venus Pencils

Venus Pencils were a brand name of pencils made by the American Lead Pencil Company beginning in 1905. The production of Venus pencils gave the company an early start in the manufacture of high-quality pencils marketed to artists and architects. Venus pencils became more popular after the First World War, which had interrupted the supply of pencil from German companies. Venus Pencils were produced in a total of seventeen degrees under the categories of soft, medium and hard, they were made with a tip and eraser, or an oversized tip and eraser. In 1956, the American Lead Pencil Company changed its name to the Venus Pen and Pencil Corporation. A number of acquisitions followed, in 1967, the company name was changed to Venus-Esterbrook. In 1973, the company was acquired by Faber-Castell. Esterbrook - An American Lead Pencil Company photo list. Http://www.pencilpages.com/mfg/amer.htm- A brief description of The American Lead Pencil Company history. - Early history of Venus pencils and different varieties of Venus pencils