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Stored Program Control
Stored program control (SPC) is a telecommunications technology for telephone exchanges. Its characteristic is that the switching system is controlled by a computer program stored in a memory in the switching system. SPC was the enabling technology of electronic switching systems (ESS) developed in the Bell System in the 1950s, and may be considered the third generation of switching technology. Stored program control was invented in 1954 by Bell Labs scientist Erna Schneider Hoover, who reasoned that computer software could control the connection of telephone calls. History Proposed and developed in the 1950s, SPC was introduced in production electronic switching systems in the 1960s. The 101ESS private branch exchange (PBX) was a transitional switching system in the Bell System to provide expanded services to business customers that were otherwise still served by an electromechanical central office switch. The first central office switch with SPC was installed at Morris, Ill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone Exchange
A telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital systems to establish telephone calls between subscribers. In historical perspective, telecommunication terms have been used with different semantics over time. The term ''telephone exchange'' is often used synonymously with ''central office'', a Bell System term. Often, a ''central office'' is defined as a building used to house the inside plant equipment of potentially several telephone exchanges, each serving a certain geographical area. Such an area has also been referred to as the exchange or exchange area. In North America, a central office location may also be identified as a ''wire center'', designating a facility to which a telephone is connected and obtains dial tone. For business and billing purposes, telecommunication carriers defi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-division Multiplexing
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern. This method transmits two or more digital signals or analog signals over a common channel. It can be used when the bit rate of the transmission medium exceeds that of the signal to be transmitted. This form of signal multiplexing was developed in telecommunications for telegraphy systems in the late 19th century, but found its most common application in digital telephony in the second half of the 20th century. History Time-division multiplexing was first developed for applications in telegraphy to route multiple transmissions simultaneously over a single transmission line. In the 1870s, Émile Baudot developed a time-multiplexing system of multiple Hughes telegraph machines. In 1944, the Britis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flying-spot Store
The flying-spot store was an optical digital memory used in early stored program control components of electronic switching systems. The flying-spot store used a photographic plate as the store of binary data. Each ''spot'' on the plate was an opaque (logical 0) or transparent (logical 1) area that stored one bit. Spots were read and written with an optical mechanism with an access time of ca. one microsecond. The optical system consisted of a cathode ray tube that functioned as a flying-spot scanner, the source of light beams produced on its face and focused onto the photographic plates with a system of lenses. A photomultiplier detected the light beam. The light beam could be split into several components to read multiple plates simultaneously, permitting the formation of a group of bits for each location. A flying-spot store was the main permanent program and data memory for the first electronic central office installed on a trial basis in Morris, Illinois in 1960. The memor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morris, Illinois
Morris is a city in and the county seat of Grundy County, Illinois, United States and part of the southwest Chicago metropolitan area. The population was estimated at 15,053 in 2019. Description Morris is the Grundy County seat and has a large hospital and modern schools. It is home to the Morris Community High School Redskins, who have won three state championships in football. There are many small parks, ball diamonds, tennis courts, two golf courses, an outdoor swimming pool, an indoor olympic-sized pool as well as the Gebhard Woods State Park and the William G. Stratton State Park for boat launching on the Illinois River and a skatepark located near White Oak elementary school. Morris Community High School is known to be located on an abandoned mining network that stems for approximately . Morris is home to the Grundy County Speedway, and the city also hosts the annual Grundy County Fair and Grundy County Corn Festival. Geography Morris is located in northeast Grundy Count ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fault-tolerant Design
Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the severity of the failure, as compared to a naively designed system, in which even a small failure can cause total breakdown. Fault tolerance is particularly sought after in high-availability, mission-critical, or even life-critical systems. The ability of maintaining functionality when portions of a system break down is referred to as graceful degradation. A fault-tolerant design enables a system to continue its intended operation, possibly at a reduced level, rather than failing completely, when some part of the system fails. The term is most commonly used to describe computer systems designed to continue more or less fully operational with, perhaps, a reduction in throughput or an increase in response time in the event of some partial f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Memory
In computing, memory is a device or system that is used to store information for immediate use in a computer or related computer hardware and digital electronic devices. The term ''memory'' is often synonymous with the term ''primary storage'' or '' main memory''. An archaic synonym for memory is store. Computer memory operates at a high speed compared to storage that is slower but less expensive and higher in capacity. Besides storing opened programs, computer memory serves as disk cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as not needed by running software. If needed, contents of the computer memory can be transferred to storage; a common way of doing this is through a memory management technique called ''virtual memory''. Modern memory is implemented as semiconductor memory, where data is stored within memory cells built from MOS transistors and other components on an integrated c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stored-program Computer
A stored-program computer is a computer that stores program instructions in electronically or optically accessible memory. This contrasts with systems that stored the program instructions with plugboards or similar mechanisms. The definition is often extended with the requirement that the treatment of programs and data in memory be interchangeable or uniform. Description In principle, stored-program computers have been designed with various architectural characteristics. A computer with a von Neumann architecture stores program data and instruction data in the same memory, while a computer with a Harvard architecture has separate memories for storing program and data. However, the term ''stored-program computer'' is sometimes used as a synonym for the von Neumann architecture. Jack Copeland considers that it is "historically inappropriate, to refer to electronic stored-program digital computers as 'von Neumann machines'". Hennessy and Patterson wrote that the early Harvard m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VoIP
Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet telephony, broadband telephony, and broadband phone service specifically refer to the provisioning of communications services (voice, fax, SMS, voice-messaging) over the Internet, rather than via the public switched telephone network (PSTN), also known as plain old telephone service (POTS). Overview The steps and principles involved in originating VoIP telephone calls are similar to traditional digital telephony and involve signaling, channel setup, digitization of the analog voice signals, and encoding. Instead of being transmitted over a circuit-switched network, the digital information is packetized and transmission occurs as IP packets over a packet-switched network. They transport media streams using special media delivery protocols t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Softswitch
A softswitch (''software switch'') is a call-switching node in a telecommunications network, based not on the specialized switching hardware of the traditional telephone exchange, but implemented in software running on a general-purpose computing platform. Like its traditional counterparts it connects telephone calls between subscribers or other switching systems across a telecommunication network. Often a softswitch is implemented to switch calls using voice over IP (VoIP) technologies, but hybrid systems exist. Although the term ''softswitch'' technically refers to any such device, it is conventionally applied to a device that handles IP-to-IP phone calls, while the phrase '' access server'' or "media gateway" is used to refer to devices that either originate or terminate traditional land line phone calls. In practice, such devices can often do both. An access server might take a mobile call or a call originating from a traditional telephone line, convert it to IP traffic, then s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CODEC
A codec is a device or computer program that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or data stream, and hence is a type of codec. ''Endec'' is a portmanteau of encoder/decoder. A coder or encoder encodes a data stream or a signal for transmission or storage, possibly in encrypted form, and the decoder function reverses the encoding for playback or editing. Codecs are used in videoconferencing, streaming media, and video editing applications. History In the mid-20th century, a codec was a device that coded analog signals into digital form using pulse-code modulation (PCM). Later, the name was also applied to software for converting between digital signal formats, including companding functions. Examples An audio codec converts analog audio signals into digital signals for transmission or encodes them for storage. A receiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System X (telephony)
System X is the digital switching system installed in telephone exchanges throughout the United Kingdom, from 1980 onwards. History Development System X was developed by the Post Office (later to become British Telecom), GEC, Plessey, and Standard Telephones and Cables (STC), and was first shown in public in 1979 at the Telecom 79 exhibition in Geneva, Switzerland. STC withdrew from the project in 1982. In 1988, the telecommunications divisions of GEC and Plessey merged to form GPT, with Plessey subsequently being bought out by GEC and Siemens. In the late 1990s, GEC acquired Siemens' 40% stake in GPT. GEC renamed itself Marconi in 1999. When Marconi was sold to Ericsson in January 2006, Telent plc retained System X and continues to support and develop it as part of its UK services business. Implementation The first System X unit to enter public service was in September 1980 and was installed in Baynard House, London and was a 'tandem junction unit' which switched tele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alcatel (mobile Device Brand)
Alcatel (formerly Alcatel Mobile Phones and Alcatel OneTouch) (previously ALCATEL) is a French brand of mobile handsets owned by Finnish consumer electronics company Nokia and used under license by Chinese electronics company TCL Technology. The Alcatel brand was licensed in 2005 by former French electronics and telecommunications company Alcatel-Lucent to TCL for mobile phones and devices, and the current license expires at the end of 2024. Nokia acquired the assets of Alcatel-Lucent in 2016 and thus also inherited the licensing agreements for the Alcatel brand. History Alcatel Mobile Phones was established on 24 April 2004 as a joint venture between Alcatel-Lucent (45%) and TCL Corporation (55%). Alcatel originally started making mobile phones in late 1996. In 2005, the joint venture was dissolved and TCL acquired Alcatel-Lucent's 45 percent share, and Alcatel Mobile Phones became a wholly owned subsidiary group of TCL. The brand name was licensed to TCL. In 2010, Alcatel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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