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Telebit
Telebit Corporation was a US-based modem manufacturer, known for their TrailBlazer series of high-speed modems. One of the first modems to routinely exceed 9600 bit/s speeds, the TrailBlazer used a proprietary modulation scheme that proved highly resilient to interference, earning the product an almost legendary reputation for reliability despite mediocre (or worse) line quality. They were particularly common in Unix installations in the 1980s and 1990s. The high price of the Telebit modems was initially not a concern as their performance was equally high compared to other systems. However, as new designs using V.32 and V.32bis began to arrive in the early 1990s, Telebit's price/performance ratio was seriously eroded. A series of new designs followed, but these never regained their performance lead. By the mid-1990s the company had been part of a series of mergers and eventually disappeared in 1998 after being acquired by Digi International. Startup Telebit was founded by Paul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microcom Networking Protocol
The Microcom Networking Protocols, almost always shortened to MNP, is a family of error-correcting protocols commonly used on early high-speed (2400 bit/s and higher) modems. Originally developed for use on Microcom's own family of modems, the protocol was later openly licensed and used by most of the modem industry, notably the "big three", Telebit, USRobotics and Hayes. MNP was later supplanted by V.42bis, which was used almost universally starting with the first V.32bis modems in the early 1990s. Overview Although XMODEM was introduced 1977, as late as 1985, ''The New York Times'' described XMODEM first, then discussed MNP as a leading contender, and that 9600 baud modems "are beginning to make their appearance." By 1988, the ''Times'' was talking about 9600 and 19.2K, and that "At least 100 other brands of modems follow" MNP (compared to Hayes's use of LAP-B). Error correction basics Modems are, by their nature, error-prone devices. Noise on the telephone line, a common oc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
XMODEM
XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. It allowed users to transmit files between their computers when both sides used MODEM. Keith Petersen made a minor update to always turn on "quiet mode", and called the result XMODEM. XMODEM, like most file transfer protocols, breaks up the original data into a series of " packets" that are sent to the receiver, along with additional information allowing the receiver to determine whether that packet was correctly received. If an error is detected, the receiver requests that the packet be re-sent. A string of bad packets causes the transfer to abort. XMODEM became extremely popular in the early bulletin board system (BBS) market, largely because it was simple to implement. It was also fairly inefficient, and as modem speeds increased, this problem led to the development of a number of modified versions of XMODEM to improve performance or address ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UUCP
UUCP (Unix-to-Unix Copy) is a suite of computer programs and communications protocol, protocols allowing remote execution of commands and transfer of computer file, files, email and netnews between computers. A command named is one of the programs in the suite; it provides a user interface for requesting file copy operations. The UUCP suite also includes (user interface for remote command execution), (the communication program that performs the file transfers), (reports statistics on recent activity), (execute commands sent from remote machines), and (reports the UUCP name of the local system). Some versions of the suite include uuencoding, / (convert 8-bit binary files to 7-bit text format and vice versa). Although UUCP was originally developed on Unix in the 1970s and 1980s, and is most closely associated with Unix-like systems, UUCP implementations exist for several non-Unix-like operating systems, including DOS, OS/2, OpenVMS (for VAX hardware only), AmigaOS, classic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paul Baran
Paul Baran (born Pesach Baran ; April 29, 1926 – March 26, 2011) was a Polish-American engineer who was a pioneer in the development of computer networks. He was one of the two independent inventors of packet switching, which is today the dominant basis for data communications in computer networks worldwide, and went on to start several companies and develop other technologies that are an essential part of modern Data communication, digital communication. Early life He was born in Grodno (then in the Second Polish Republic, and since 1945 part of Belarus) on April 29, 1926. He was the youngest of three children in his Lithuanian Jews, Lithuanian Jewish family, with the Yiddish given name "Pesach". His family moved to the United States on May 11, 1928, settling in Boston and later in Philadelphia, where his father, Morris "Moshe" Baran (1884–1979), opened a grocery store. He graduated from Drexel University (then called Drexel Institute of Technology) in 1949, with a degree ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hayes Command Set
The Hayes command set (also known as the AT command set) is a specific command language originally developed by Dale Heatherington and Dennis Hayes for the Hayes Smartmodem in 1981. The command set consists of a series of short text strings which can be combined to produce commands for operations such as dialing, hanging up, and changing the parameters of the connection. The vast majority of dial-up modems use the Hayes command set in numerous variations. The command set covered only those operations supported by the earliest modems. When new commands were required to control additional functionality in higher speed modems, a variety of one-off standards emerged from each of the major vendors. These continued to share the basic command structure and syntax, but added any number of new commands using some sort of prefix character for Hayes and USRobotics, and for Microcom, for instance. Many of these were re-standardized on the Hayes extensions after the introduction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protocol Spoofing
Protocol spoofing is used in data communications to improve performance in situations where an existing protocol is inadequate, for example due to long delays or high error rates. Spoofing techniques In most applications of protocol spoofing, a communications device such as a modem or router simulates ("spoofs") the remote endpoint of a connection to a locally attached host, while using a more appropriate protocol to communicate with a compatible remote device that performs the equivalent spoof at the other end of the communications link. File transfer spoofing Error correction and file transfer protocols typically work by calculating a checksum or CRC for a block of data known as a ''packet'', and transmitting the resulting number at the end of the packet. At the other end of the connection, the receiver re-calculates the number based on the data it received and compares that result to what was sent from the remote machine. If the two match the packet was transmitted correctl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthogonal Frequency-division Multiplexing
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission used in digital modulation for encoding digital (binary) data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL internet access, wireless networks, power line networks, and 4G/ 5G mobile communications. OFDM is a frequency-division multiplexing (FDM) scheme that was introduced by Robert W. Chang of Bell Labs in 1966. In OFDM, the incoming bitstream representing the data to be sent is divided into multiple streams. Multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted, with each carrier modulated with bits from the incoming stream so multiple bits are being transmitted in parallel. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet
The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks that consists of Private network, private, public, academic, business, and government networks of local to global scope, linked by a broad array of electronic, Wireless network, wireless, and optical networking technologies. The Internet carries a vast range of information resources and services, such as the interlinked hypertext documents and Web application, applications of the World Wide Web (WWW), email, electronic mail, internet telephony, streaming media and file sharing. The origins of the Internet date back to research that enabled the time-sharing of computer resources, the development of packet switching in the 1960s and the design of computer networks for data communication. The set of rules (communication protocols) to enable i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comparison Of Synchronous And Asynchronous Signalling
Synchronous and asynchronous transmissions are two different methods of transmission synchronization. Synchronous transmissions are synchronized by an external clock, while asynchronous transmissions are synchronized by special signals along the transmission medium. The need for synchronization Whenever an electronic device transmits digital (and sometimes analogue) data to another, there must be a certain rhythm established between the two devices, i.e., the receiving device must have some way of, within the context of the fluctuating signal that it's receiving, determining where each unit of data begins and where it ends. Methods of synchronization There are two ways to synchronize the two ends of the communication. The synchronous signalling methods use two different signals. A pulse on one signal indicates when another bit of information is ready on the other signal. The asynchronous signalling methods use only one signal. The receiver uses transitions on that signal to f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motorola 68000
The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector. The design implements a 32-bit instruction set, with 32-bit registers and a 16-bit internal data bus. The address bus is 24 bits and does not use memory segmentation, which made it easier to program for. Internally, it uses a 16-bit data arithmetic logic unit (ALU) and two more 16-bit ALUs used mostly for addresses, and has a 16-bit external data bus. For this reason, Motorola termed it a 16/32-bit processor. As one of the first widely available processors with a 32-bit instruction set, large unsegmented address space, and relatively high speed for the era, the 68k was a popular design through the 1980s. It was widely used in a new generation of personal computers with graphical user interfaces, including the Macintosh 128K, Amiga, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Texas Instruments TMS320
TMS320 is a blanket name for a series of digital signal processors (DSPs) from Texas Instruments. It was introduced on April 8, 1983, through the TMS32010 processor, which was then the fastest DSP on the market. The processor is available in many different variants, some with fixed-point arithmetic and some with floating-point arithmetic. The TMS320 processors were fabricated on MOS integrated circuit chips, including both NMOS and CMOS variants. The floating-point DSP TMS320C3x, which exploits delayed branch logic, has as many as three delay slots. This series of processors are used as a digital signal processing co-processor and as the main CPU in some applications. Newer implementations support standard IEEE JTAG control for boundary scan and/or in-circuit debugging. The original TMS32010 and its subsequent variants are an example of a CPU with a modified Harvard architecture, which features separate address spaces for instruction and data memory but the ability to read da ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synchronous Data Link Control
Synchronous Data Link Control (SDLC) is a computer serial communication, serial communications protocol first introduced by IBM as part of its Systems Network Architecture (SNA). SDLC is used as layer 2, the data link layer, in the SNA protocol stack. It supports multipoint links as well as error correction. It also runs under the assumption that an SNA header is present after the SDLC header. SDLC was mainly used by IBM mainframe and midrange systems; however, implementations exist on many platforms from many vendors. In the United States and Canada, SDLC can be found in traffic control cabinets. SDLC was released in 1975,PC Lube and Tune accessed 15. October 2009. based on work done for IBM in the early 1970s.. SDLC operates independently on each communications link in the network and can operate on point-to-poi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
