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Marker (telecommunications)
A marker is a type of special purpose control system that was used in electromechanical telephone central office switches. Switches employing markers belong to a class of switches known as "common control", as the purpose of a marker is to control the closure of contacts in the switching fabric that connect a circuit between the calling party and the called party. This is in contrast to "direct control" switches, where the switching elements were controlled directly by the customer's dial, such as the Step by Step switch. The term marker came from its use to mark a path of links through the switching fabric. A marker's comprehensive view of the switching fabric allowed it to find and assemble a path from one terminal to another, if the links were available, unlike the earlier graded progressive systems in which a path might not be found. Markers were sometimes referred to as special purpose computers, but lacking stored program control, they were not computers according to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone Exchange
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 def ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1XB Switch
The Number One Crossbar Switching System (1XB), was the primary technology for urban telephone exchanges served by the Bell System in the mid-20th century. Its switch fabric used the electromechanical crossbar switch to implement the topology of the panel switching system of the 1920s. The first No. 1 Crossbar was installed in the PResident-2 central office at Troy Avenue in Brooklyn, New York which became operational in February 1938. Evolution The predecessor to the No. 1 Crossbar was the panel system, which was used in many large metropolitan areas beginning in the early 1920s. By the 1930s, there was a growing need for a new type of switching machine that did not have the drawbacks inherent in the panel system. Desirable features of the crossbar system included: * Elimination of the motor-driven equipment * Reduction in the number of unique parts * Reduction in the cost of maintenance * Bifurcated, precious metal relay contacts, resulting in improved contact performance a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centrex
Centrex is a portmanteau of central exchange, a kind of telephone exchange. It provides functions similar to a PBX, but is provisioned with equipment owned by, and located at, the telephone company premises. Centrex service was first installed in the early 1960s in New York's financial district by New York Telephone. As of 2003, it was estimated that there were 20 million Centrex lines installed worldwide by 20 telephone companies, with the most installations in the United States (15 million), Canada (2 million), and the United Kingdom (1 million). This accounted for approximately 5% of all installed business telephone lines, worldwide. In terms of user-visible features, Centrex and PBX are similar. Features include: * Direct inward dialing (DID) * Automatic routing of calls to obtain lowest cost * Call pick-up groups * Call forwarding * Conference calling * Automatic call distribution (ACD) * Call detail recording In computer science, a record (also called a struct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calling Feature
A vertical service code (VSC) is a sequence of digits and the signals star (*) and number sign (#) dialed on a telephone keypad or rotary dial to enable or disable certain telephone service features. Some vertical service codes require dialing of a telephone number after the code sequence. On a touch tone telephone, the codes are usually initiated with the star key, resulting in the commonly used name ''star codes''. On rotary dial telephones, the star is replaced by dialing ''11''. In North American telephony, VSCs were developed by AT&T Corp. as Custom Local Area Signaling Services (CLASS or LASS) codes in the 1960s and 70s. Their use became ubiquitous throughout the 1990s and eventually became a recognized standard. As ''CLASS'' was an AT&T trademark, the term ''vertical service code'' was adopted by the North American Numbering Plan Administration. The use of ''vertical'' is a somewhat dated reference to older switching methods and the fact that these services can only be a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Class Of Service
Class of service (COS or CoS) is a parameter used in data and voice protocols to differentiate the types of payloads contained in the packet being transmitted. The objective of such differentiation is generally associated with assigning priorities to the data payload or access levels to the telephone call. Data services As related to network technology, COS is a 3- bit field that is present in an Ethernet frame header when 802.1Q VLAN tagging is present. The field specifies a priority value between 0 and 7, more commonly known as CS0 through CS7, that can be used by quality of service (QoS) disciplines to differentiate and shape/police network traffic. COS operates only on 802.1Q VLAN Ethernet at the data link layer (layer 2), while other QoS mechanisms (such as DiffServ, also known as DSCP) operate at the IP network layer (layer 3) or use a local QoS tagging system that does not modify the actual packet, such as Cisco's "QoS-Group". Network devices (i.e. routers, switches, et ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone Call
A telephone call is a connection over a telephone network between the called party and the calling party. First telephone call The first telephone call was made on March 10, 1876, by Alexander Graham Bell. Bell demonstrated his ability to "talk with electricity" by transmitting a call to his assistant, Thomas Watson. The first words transmitted were "Mr Watson, come here. I want to see you." This event has been called Bell's "greatest success", as it demonstrated the first successful use of the telephone. Although it was his greatest success, he refused to have a telephone in his own home because it was something he invented by mistake and saw it as a distraction from his main studies. Information transmission A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile transmission when they are using fax machines. The call may use land line, mobile phone, satellite p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell System
The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America for over one hundred years from its creation in 1877 until its antitrust breakup in 1983. The system of companies was often colloquially called Ma Bell (as in "Mother Bell"), as it held a vertical monopoly over telecommunication products and services in most areas of the United States and Canada. At the time of the breakup of the Bell System in the early 1980s, it had assets of $150 billion (equivalent to $ billion in ) and employed over one million people. Ever since the 1910s, American antitrust regulators had been observing and accusing the Bell System of abusing its monopoly power, and had brought legal action multiple times over the decades, until in 1974 the Antitrust Division of the U.S. Department of Justice brought a lawsuit against Be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
5XB Switch
The Number Five Crossbar Switching System (5XB switch) is a telephone switch for telephone exchanges designed by Bell Labs and manufactured by Western Electric starting in 1947. It was used in the Bell System principally as a Class 5 telephone switch in the public switched telephone network (PSTN) until the early 1990s, when it was replaced with electronic switching systems. Variants were used as combined Class 4 and Class 5 systems in rural areas, and as a TWX switch. 5XB was originally intended to bring the benefits of crossbar switching to towns and small cities with only a few thousand telephone lines. The typical starting size was 3000 to 5000 lines, but the system had essentially unlimited growth capacity. The earlier 1XB urban crossbar was impractically expensive in small installations, and had difficulties handling large trunk groups. 5XB was converted to wire spring relays in the 1950s and otherwise upgraded in the 1960s to serve exchanges with tens of thousands of l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Number One Crossbar Switching System
The Number One Crossbar Switching System (1XB), was the primary technology for urban telephone exchanges served by the Bell System in the mid-20th century. Its switch fabric used the electromechanical crossbar switch to implement the topology of the panel switching system of the 1920s. The first No. 1 Crossbar was installed in the PResident-2 central office at Troy Avenue in Brooklyn, New York which became operational in February 1938. Evolution The predecessor to the No. 1 Crossbar was the panel system, which was used in many large metropolitan areas beginning in the early 1920s. By the 1930s, there was a growing need for a new type of switching machine that did not have the drawbacks inherent in the panel system. Desirable features of the crossbar system included: * Elimination of the motor-driven equipment * Reduction in the number of unique parts * Reduction in the cost of maintenance * Bifurcated, precious metal relay contacts, resulting in improved contact performance a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Control
In telecommunications, common control is a principle of switching telephone calls in an automatic telephone exchange that employs shared control equipment which is attached to the circuit of a call only for the duration of establishing or otherwise controlling the call. Thus, such control equipment need only be provided in as few units to satisfy overall exchange traffic, rather than being duplicated for every subscriber line. In contrast, ''direct control'' systems have subsystems for call control that are an integral part of the switching network. Strowger exchanges are usually direct control systems, whereas crossbar, and electronic exchanges (including all stored program control systems) are common control systems. Common control is also known as indirect control or register control. History Early semi-mechanical installations with common control components existed, for example rotary systems in Sweden and France in 1915, and the first panel switches in Newark, New Jerse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Panel Switch
The Panel Machine Switching System is a type of automatic telephone exchange for urban service that was used in the Bell System in the United States for seven decades. The first semi-mechanical types of this design were installed in 1915 in Newark, New Jersey, and the last were retired in the same city in 1983. The Panel switch was named for its tall panels which consisted of layered strips of terminals. Between each strip was placed an insulating layer, which kept each metal strip electrically isolated from the ones above and below. These terminals were arranged in ''banks'', five of which occupied an average selector frame. Each bank contained 100 sets of terminals, for a total of 500 sets of terminals per frame. At the bottom, the frame had two electric motors to drive sixty selectors up and down by electromagnetically controlled clutches. As calls were completed through the system, selectors moved vertically over the sets of terminals until they reached the desired location, at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crossbar Switch
In electronics and telecommunications, a crossbar switch (cross-point switch, matrix switch) is a collection of switches arranged in a matrix configuration. A crossbar switch has multiple input and output lines that form a crossed pattern of interconnecting lines between which a connection may be established by closing a switch located at each intersection, the elements of the matrix. Originally, a crossbar switch consisted literally of crossing metal bars that provided the input and output paths. Later implementations achieved the same switching topology in solid-state electronics. The crossbar switch is one of the principal telephone exchange architectures, together with a rotary switch, memory switch, and a crossover switch. General properties A crossbar switch is an assembly of individual switches between a set of inputs and a set of outputs. The switches are arranged in a matrix. If the crossbar switch has M inputs and N outputs, then a crossbar has a matrix with ''M'' × ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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