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Pennywhistle Modem
The Pennywhistle was an early acoustic coupler modem originally designed and built by Lee Felsenstein in 1973, and later commercialized and offered for sale in 1976. It was one of the earliest modems available for hobbyist computer users. Like most acoustic coupler modems, the Pennywhistle was replaced by the Hayes Smartmodem and similar models from the early 1980s. History Prior modem As part of the effort that would lead to the Community Memory bulletin board system, Lee Felsenstein had found an Omnitech modem ("or something like that"). Designed to operate at rates as high as 300 bits per second (bit/s), the modem was able to change its speed to match conditions or differences in the modems at either end. In general it was good for only 100 bit/s, the speed that was used for much of its operational life. The modem was attached to a Teletype Model 33 ASR machine at Leopold's Records in Berkeley, California and connected to the SDS 940 mainframe computer in San Franci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Coupler
In telecommunications, an acoustic coupler is an interface device for coupling electrical signals by acoustical means—usually into and out of a telephone. The link is achieved through converting electric signals from the phone line to sound and reconvert sound to electric signals needed for the end terminal, such as a teletypewriter, and back, rather than through direct electrical connection. History and applications Prior to its breakup in 1984, Bell System's legal monopoly over telephony in the United States allowed the company to impose strict rules on how consumers could access their network. Customers were prohibited from connecting equipment not made or sold by Bell to the network. The same set-up was operative in nearly all countries, where the telephone companies were nationally owned. In many households, telephones were hard-wired to wall terminals before connectors like RJ11 and BS 6312 became standardized. The situation was similar in other countries. In Australi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal representing sound or a video signal representing images, in an electronic device or communication channel. Distortion is usually unwanted, and so engineers strive to eliminate or minimize it. In some situations, however, distortion may be desirable. For example, in noise reduction systems like the Dolby system, an audio signal is deliberately distorted in ways that emphasize aspects of the signal that are subject to electrical noise, then it is symmetrically "undistorted" after passing through a noisy communication channel, reducing the noise in the received signal. Distortion is also used as a musical effect, particularly with electric guitars. The addition of noise or other outside signals (hum, interference) is not considered di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Western Electric
The Western Electric Company was an American electrical engineering and manufacturing company officially founded in 1869. A wholly owned subsidiary of American Telephone & Telegraph for most of its lifespan, it served as the primary equipment manufacturer, supplier, and purchasing agent for the Bell System from 1881 to 1984 when it was dismantled. The company was responsible for many technological innovations as well as developments in industrial management. History In 1856, George Shawk, a craftsman and telegraph maker, purchased an electrical engineering business in Cleveland, Ohio. In January, 1869, Shawk had partnered with Enos M. Barton in the former Western Union repair shop of Cleveland, to manufacture burglar, fire alarms, and other electrical items. Both men were former Western Union employees. Shawk, was the Cleveland shop foreman and Barton, was a Rochester, New York telegrapher. During this Shawk and Barton partnership, one customer was an inventor sourcing parts an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Novation CAT
Novation, in contract law and business law, is the act of – # replacing an obligation to perform with another obligation; or # adding an obligation to perform; or # replacing a party to an agreement with a new party. In international law, novation is the acquisition of territory by a sovereign state through "the gradual transformation of a right ''in territorio alieno'' n foreign territoryinto full sovereignty without any formal and unequivocal instrument to that effect intervening".John P. Grant and J. Craig Barker (eds.), "Novation", in ''Perry & Grant Encyclopaedic Dictionary of International Law'', 3rd ed. (Oxford University Press, 2009). Origins in Roman law Novati, as a legal term is derived from the Roman law, in which ''novatio'' was of three kinds—substitution of a new debtor (''expromissio'', or ''delegatio''), of a new creditor (''cessio nominum vel actionum''), or of a new contract. In English law the term (though it occurs as early as Bracton) is scarcely na ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Popular Electronics
''Popular Electronics'' was an American magazine published by John August Media, LLC, and hosted at TechnicaCuriosa.com. The magazine was started by Ziff-Davis Publishing Company in October 1954 for electronics hobbyists and experimenters. It soon became the "World's Largest-Selling Electronics Magazine". In April 1957 Ziff-Davis reported an average net paid circulation of 240,151 copies. ''Popular Electronics'' was published until October 1982 when, in November 1982, Ziff-Davis launched a successor magazine, ''Computers & Electronics''. During its last year of publication by Ziff-Davis, ''Popular Electronics'' reported an average monthly circulation of 409,344 copies. The title was sold to Gernsback Publications, and their '' Hands-On Electronics'' magazine was renamed to ''Popular Electronics'' in February 1989, and published until December 1999. The Popular Electronics trademark was then acquired by John August Media, who revived the magazine, the digital edition of which is hos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schematic
A schematic, or schematic diagram, is a designed representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the key information the schematic is intended to convey, and may include oversimplified elements in order to make this essential meaning easier to grasp, as well as additional organization of the information. For example, a subway map intended for passengers may represent a subway station with a dot. The dot is not intended to resemble the actual station at all but aims to give the viewer information without unnecessary visual clutter. A schematic diagram of a chemical process uses symbols in place of detailed representations of the vessels, piping, valves, pumps, and other equipment that compose the system, thus emphasizing the functions of the individual elements and the interconnections among them and suppresses their physical details. In an electronic circuit d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VDM-1
The Processor Technology VDM-1, for Video Display Module, was the first video card for S-100 bus computers. Created in 1975, it allows an S-100 machine to produce its own display, and when paired with a keyboard and their 3P+S card, it eliminates the need for a separate video terminal. Using a 7 x 9 dot matrix and ASCII characters, it produces a 64-column by 16-row text display. The VDM-1 is a complex card and was soon replaced by an increasing number of similar products from other companies. An early competitor was the Solid State Music VB-1, which offers an identical display from a much simpler card. Later cards using LSI chips have enough room to include the keyboard controller as well. History TV Typewriter In September 1973, the cover article of Radio Electronics magazine was Don Lancaster's "Build a TV Typewriter", which allows users to type characters on a keyboard and have them appear on a conventional television. Given this limited functionality, they initially estimate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Terminal
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and predated the use of a computer screen by decades. Early terminals were inexpensive devices but very slow compared to punched cards or paper tape for input, yet as the technology improved and video displays were introduced, terminals pushed these older forms of interaction from the industry. A related development was time-sharing systems, which evolved in parallel and made up for any inefficiencies in the user's typing ability with the ability to support multiple users on the same machine, each at their own terminal or terminals. The function of a terminal is typically confined to transcription and input of data; a device with significant local, programmable data-processing capability may be called a "smart terminal" or fat client. A te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phase Locked Loop
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. There are several different types; the simplest is an electronic circuit consisting of a variable frequency oscillator and a phase detector in a feedback loop. The oscillator's frequency and phase are controlled proportionally by an applied voltage, hence the term voltage-controlled oscillator (VCO). The oscillator generates a periodic signal of a specific frequency, and the phase detector compares the phase of that signal with the phase of the input periodic signal, to adjust the oscillator to keep the phases matched. Keeping the input and output phase in lockstep also implies keeping the input and output frequencies the same. Consequently, in addition to synchronizing signals, a phase-locked loop can track an input frequency, or it can generate a frequency that is a multiple of the input frequency. These properties are use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ampex
Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff as a spin-off of Dalmo-Victor. The name AMPEX is a portmanteau, created by its founder, which stands for Alexander M. Poniatoff Excellence.AbramsoThe History of television, 1942 to 2000– McFarland, 2003 – , page 286, Chapter 2, footnote 34 "1944 he founded Ampex (the name was created from his initials, AMP, plus "ex" for excellence)" Today, Ampex operates as Ampex Data Systems Corporation, a subsidiary of Delta Information Systems, and consists of two business units. The Silicon Valley unit, known internally as Ampex Data Systems (ADS), manufactures digital data storage systems capable of functioning in harsh environments. The Colorado Springs, Colorado unit, referred to as Ampex Intelligent Systems (AIS), serves as a laboratory and hub for the company's line of industrial control systems, cyber security products and services and its artificial intelligence/machine learning technology. Am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baud Rate
In telecommunication and electronics, baud (; symbol: Bd) is a common unit of measurement of symbol rate, which is one of the components that determine the speed of communication over a data channel. It is the unit for symbol rate or modulation rate in symbols per second or pulses per second. It is the number of distinct symbol changes (signalling events) made to the transmission medium per second in a digitally modulated signal or a bd rate line code. Baud is related to ''gross bit rate'', which can be expressed in bits per second. If there are precisely two symbols in the system (typically 0 and 1), then baud and bit per second (bit/s) are equivalent. Naming The baud unit is named after Émile Baudot, the inventor of the Baudot code for telegraphy, and is represented according to the rules for SI units. That is, the first letter of its symbol is uppercase (Bd), but when the unit is spelled out, it should be written in lowercase (baud) except when it begins a sentence. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
