|
In the field of telecommunications, a central office or telephone exchange houses equipment that is commonly known as simply a switch, which is a piece of equipment that connects phone calls. It is what makes phone calls "work" in the sense of making connections and relaying the speech information. Image File history File links LinkFA-star. ...
Telecommunication is the extension of communication over a distance. ...
The term exchange can also be used to refer to an area served by a particular switch. And more narrowly, it can refer to the first three digits of the local number.
In the past, the first two or three digits would map to a mnemonic exchange name, e.g. 869–1234 was formerly TOwnsend 9–1234, and before that (in some localities) might have been TOWnsend 1234 (only the capital letters and numbers being dialed).
In December of 1930, New York City became the first locality in the United States to adopt the two-letter, five-number format; it remained alone in this respect until well after World War II, when other municipalities across the country began to follow suit (in some areas, most notably much of California, telephone numbers in the 1930s through early 1950s consisted of only six digits, two letters which began the exchange name followed by four numbers, as in DUnkirk 0799). Prior to the mid-1950s, the number immediately following the name could never be a "0" or "1;" indeed, "0" was never pressed into service at all, except in the immediate Los Angeles area (the "BEnsonhurst 0" exchange mentioned in an episode of the popular TV sitcom The Honeymooners was fictitious). Look up December in Wiktionary, the free dictionary. ...
1930 (MCMXXX) is a common year starting on Wednesday. ...
Nickname: The Big Apple Motto: Official website: City of New York Location [[Image:|250px|250px|Location of City of New York, New York]] Location in the state of New York Government Counties (Boroughs) Bronx (The Bronx) New York (Manhattan) Queens (Queens) Kings (Brooklyn) Richmond (Staten Island) Mayor Michael Bloomberg (R...
Combatants Allied Powers Axis Powers Commanders {{{commander1}}} {{{commander2}}} Strength {{{strength1}}} {{{strength2}}} Casualties 17 million military deaths 8 million military deaths {{{notes}}} World War II, also known as the Second World War, was a military conflict that took place between 1939 and 1945. ...
Official language(s) English Capital Sacramento Largest city Los Angeles Area - Total - Width - Length - % water - Latitude - Longitude Ranked 3rd 410,000 km² 402. ...
// Events and trends A public speech by Benito Mussolini, founder of the Fascist movement The 1930s were described as an abrupt shift to more radical lifestyles, as countries were struggling to find a solution to the global depression. ...
// Events and trends This map shows two essential global spheres during the Cold War in 1959. ...
// Events and trends This map shows two essential global spheres during the Cold War in 1959. ...
Nickname: City of Angels Motto: Official website: http://www. ...
Cover of a book about the Honeymooners. ...
In 1955, the Bell System attempted to standardize the process of naming exchanges by issuing a "recommended list" of names to be used for the various number combinations. In 1961, New York Telephone introduced "selected-letter" exchanges, in which the two letters did not mark the start of any particular name (example: FL 6-9970), and by 1965 all newly-connected phone numbers nationwide consisted of numerals only (Wichita Falls, Texas had been the first locality in the United States to implement the latter, having done so in 1958) Pre-existing numbers continued to be displayed the old way in many places well into the 1970s. A Chicago carpet retailer frequently advertised their number NAtional 2-9000 on WGN until the 1990s; not to mention, the number TYler 8-7100 for a Detroit construction company. 1955 (MCMLV in Roman) was a common year starting on Saturday of the Gregorian calendar. ...
The Bell System was a trademark and service mark used by the US telecommunications company American Telephone & Telegraph Company (AT&T) and its affiliated companies to co-brand their extensive circuit-switched telephone network and their affiliations with each other. ...
1961 (MCMLXI) was a common year starting on Sunday (link will take you to calendar). ...
1965 (MCMLXV) was a common year starting on Friday (link goes to calendar). ...
Wichita Falls is a city in Wichita County, Texas, United States. ...
1958 (MCMLVIII) was a common year starting on Wednesday of the Gregorian calendar. ...
The 1970s decade refers to the years from 1970 to 1979, inclusive. ...
Chicago (officially named the City of Chicago) is the third largest city in the United States (after New York City and Los Angeles), with an official population of 2,896,016, as of the 2000 census. ...
WGN is the callsign of two broadcast stations in Chicago, Illinois, both owned by the Tribune company. ...
The 1990s decade refers to the years from 1990 to 1999, inclusive, the last decade of the 20th Century. ...
Motto: Speramus Meliora; Resurget Cineribus (We Hope For Better Things; It Shall Rise From the Ashes - this motto was adopted after the disastrous 1805 fire that devastated the city) Nickname: The Motor City and Motown Location in Wayne County, Michigan Founded Incorporated July 24, 1701 1815 County Wayne County Mayor...
Most of the United Kingdom had no lettered telephone dials until the introduction of Subscriber Trunk Dialling (STD) in 1958. Only the director areas (Birmingham, Edinburgh, Glasgow, Liverpool, London and Manchester) and the non-director areas adjacent to them had lettered dials, and the exchanges used the three-letter, four-number format until conversion to all-figure numbering in 1968. Subscriber trunk dialling (STD) (also known as subscriber toll dialling) is an obsolete term for the UK telephone system allowing subscribers to dial trunk calls without operator assistance. ...
1958 (MCMLVIII) was a common year starting on Wednesday of the Gregorian calendar. ...
The Director System was introduced to six cities in the UK from 1922 following the introduction of the automatic telephone exchange in the UK in 1912. ...
1968 (MCMLXVIII) was a leap year starting on Monday (the link is to a full 1968 calendar). ...
In the United States, the word exchange can also have the technical meaning of a local access and transport area under the Modification of Final Judgment (MFJ). Local access and transport area (LATA) is a term used in U.S. telecommunications regulation. ...
In telecommunication, Modification of Final Judgment (MFJ) is the 1982 antitrust suit settlement agreement (consent decree) entered into by the United States Department of Justice and the American Telephone and Telegraph Company (AT&T) that, after modification and upon approval of the United States District Court for the District of...
Historic perspective
 A telephone operator manually connected calls with patch cables at a telephone switchboard. Computers make most connections now. (Telephone switchboard photograph courtesy of JoeTourist InfoSystems) The first telephone exchange opened in New Haven, Connecticut in 1878. The switchboard was built from "carriage bolts, handles from teapot lids and bustle wire" and could handle two simultaneous conversations (see National Park Service). © This image is copyrighted. ...
© This image is copyrighted. ...
A telephone operator at work on a private switchboard A telephone operator is either a person who provides assistance to a telephone caller, usually in the placing of operator assisted telephone calls such as calls from a pay phone, collect calls (called reversed-charge calls in the UK), calls which...
Nickname: The Elm City Motto: Official website: www. ...
1878 was a common year starting on Tuesday (see link for calendar). ...
Later exchanges consisted of one to several hundred plug boards manned by operators. Each operator sat in front of from one to three banks of ¼-inch phone jacks fronted by several rows of phone cords, each of which was the local termination of a phone subscriber line. A calling party (known as the 'subscriber'), would lift the receiver, a light near the plug would light, and the operator would switch into the circuit to ask "number please?". Depending upon the answer, the operator might plug the plug into a local jack and start the ringing cycle, or plug into a hand-off circuit to start what might be a long distance call handled by subsequent operators in another bank of boards or in another building miles away. Telephone switchboard, 1974 A switchboard (also called a manual branch exchange) is a device used to manually connect a group of telephones from one to another or to an outside connection. ...
A telephone operator at work on a private switchboard A telephone operator is either a person who provides assistance to a telephone caller, usually in the placing of operator assisted telephone calls such as calls from a pay phone, collect calls (called reversed-charge calls in the UK), calls which...
Subscriber: In a public switched telecommunications network such as the common telephone system, the ultimate user, customer, of a communications service. ...
The person who (or device that) initiates a telephone call over the public switched telephone network is the calling party. ...
On March 10, 1891, Almon Strowger, an undertaker in Topeka, Kansas, patented the Strowger switch, a device which led to the automation of the telephone circuit switching. While there were many extensions and adaptations of this initial patent, the one best known consists of 10 layers or banks of 10 contacts arranged in a semi-circle. When used with a dial telephone, each pair of numbers caused the shaft of the central contact "hand" to first step up a layer per digit and then swing in a contact row per digit. March 10 is the 69th day of the year in the Gregorian Calendar (70th in Leap years). ...
1891 (MDCCCXCI) was a common year starting on Thursday (see link for calendar). ...
Almon Brown Strowger (1839 – May 26, 1902) gave his name to the electromechanical telephone exchange technology that his invention and patent inspired. ...
Almon Brown Strowger (1839 - May 26, 1902) gave his name to the electromechanical telephone exchange technology that his invention and patent inspired. ...
These step switches were arranged in banks, beginning with a "line-finder" which detected that one of up to a hundred subscriber lines had the receiver lifted "off hook". The line finder hooked the subscriber to a "dial tone" bank to show that it was ready. The subscriber's dial pulsed at 10 pulses per second (depending on standards in particular countries). In electrical controls, a stepping switch (also called a uniselector; see Strowger switch, below) is an electromechanical device used, most prominently, in early automatic telephone exchanges to route calls. ...
Exchanges based on the Strowger switch were challenged by crossbar technology. These phone exchanges promised faster switching and would accept pulses faster than the Strowger's typical 10 pps — typically about 20 pps. The advent of dual-tone multifrequency (DTMF) tone-signalling solid-state switches (i.e., touch tone dialling) cut off the crossbar's takeover before it could really get going. A crossbar switch is an electromechanical device for switching telephone calls. ...
Dual-tone multi-frequency (DTMF), also known as Touch Tone® is used for telephone signaling over the line in the voice frequency band to the call switching center. ...
A transitional technology (from pulse to DTMF) had DTMF "link finders" which converted DTMF to pulse and fed it to conventional strowger or crossbar switches. This technology was used as late as the mid to late 1990s. This article is about the year. ...
Historic trivia Because the switches were hard-wired together and fairly hard to re-wire (re-grade), telephone exchange buildings in many larger cities were dedicated to circuits that began with the first two or three numbers of the (in North America) standard 7 digit phone numbers. In a holdover from the days of plug-board exchanges, the exchanges were typically named with a name whose first two letters translated to the digits of the exchange's prefix on a common telephone dial. Examples: CAstle (22), TRinity (87), MUtual (68). Certain number combinations were not amenable to this naming process, such as "57," "95" and "97;" it was in part due to this factor that the name system was eventually abandoned, as more numbers were needed to prevent a given area code from running out of available numbers. A telephone numbering plan is a system that allows subscribers to make and receive telephone calls across long distances. ...
Because the pulses in a Strowger switch exchange took time, having a phone number with lots of 8s or 9s or 0s meant it took longer to dial. The phone companies typically assigned such "high" numbers to pay phones because they were rarely dialed to.
To test the basic functioning of all of the switches in a chain, a special "test" number was reserved that consisted of all 5s (555–5555) — half-way up and in on each bank. The "555" (or KLondike) exchange was never assigned any real numbers, which is why today's TV and movie shows use 555-xxxx numbers for their phone numbers (previously, such productions often used numbers that ended in certain four-number combinations that were typically set aside for similar uses — "0079" on the West Coast and "9970" in many other places; examples include the TV series Perry Mason and the 1948 film Sorry, Wrong Number). That way there was no possibility that a fake number from a show would actually reach someone, thus avoiding the scenario which arose in 1982 with Tommy Tutone's hit single 867-5309/Jenny, which led to many customers who actually had that number receiving a plethora of unwanted calls. In fact, many US phone companies either no longer assign this number, or have relegated it to internal testing purposes. Perry Mason is a fictional defense attorney who originally appeared in detective fiction by Erle Stanley Gardner. ...
1948 (MCMXLVIII) is a leap year starting on Thursday (link will take you to calendar). ...
Categories: Movie stubs | 1948 films | 1989 films | Best Actress Oscar Nominee (film) ...
1982 (MCMLXXXII) is a common year starting on Friday of the Gregorian calendar. ...
Tommy Tutone is a rock band from San Francisco, California, best known for its 1982 hit 867-5309/Jenny, which peaked at #4 on the Billboard pop charts. ...
867-5309/Jenny is the name of a song written by Alex Call and Jim Keller and performed by Tommy Tutone which peaked at Number 4 on the Billboard Pop Singles chart in 1982 (see 1982 in music). ...
However, today only numbers beginning with 555–01 are reserved for fiction and other 555-numbers can be allocated to "information providers". A side effect of the fictional-number pool being reduced to 100 numbers is that the same ones now often recur in different movies or TV shows. The "958" and "959" exchanges have also been reserved for similar purposes in most localities, and as a result very few individuals or businesses have telephone numbers beginning with those sets of digits either (although this fact is not as well known, so such numbers have not been used in a fictional context).
The number in the Glenn Miller Orchestra's hit 'PEnnsylvania 6-5000' was and is the number of the Hotel Pennsylvania in New York. If you call the number, now written as (212) 736-5000, you still get the hotel.
Technologies In U.S. and military telecommunication, a digital switch is a switch that performs time-division multiplexing switching of digitized signals. Source: from Federal Standard 1037C and from MIL-STD-188. All switches built since the 1980s are digital, so for practical purposes this is a distinction without a difference. This article describes digital switches, including algorithms and equipment. BlackBerry 7100t Telecommunication refers to communication over long distances. ...
It has been suggested that switching be merged into this article or section. ...
Time-division multiplexing (TDM) is a type of digital multiplexing in which two or more apparently simultaneous channels are derived from a given frequency spectrum, i. ...
Switching is an action described by the verb to switch, in the sense of using a Switch, either an electrical one or other device for flipping, or a rod called switch. ...
Federal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U.S. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ...
MIL-STD-188 is a series of U.S. military standards relating to telecommunications. ...
This article will use the terms:
- telephone exchange for the building
- telephone switch for the switching equipment
- concentrator for the concentrator, whether or not it is co-located with the switch
Manual telephone exchanges With all-manual calling, the customer calls the operator and asks the operator for the number, and provided that the number is in the same central office, the operator connects the call by plugging into the jack on the switchboard corresponding to that customer's line. If the call is to another central office, the operator plugs into the trunk for the other office and asks the operator answering (known as the "inward" operator) to connect the call. A telephone operator at work on a private switchboard A telephone operator is either a person who provides assistance to a telephone caller, usually in the placing of operator assisted telephone calls such as calls from a pay phone, collect calls (called reversed-charge calls in the UK), calls which...
Telephone switchboard, 1974 A switchboard (also called a manual branch exchange) is a device used to manually connect a group of telephones from one to another or to an outside connection. ...
Most manual telephone exchanges in cities were common-battery, meaning that the central office provided power for the telephone circuits, as is the case today. A customer lifting their receiver would change their line status to "tip," thereby lighting a light on the operator's switchboard. In smaller towns, early telephones were often magneto, or crank, phones, where the subscriber turned a crank to generate current to activate the "tip" condition, notifying the operator of the call. Batteries at the subscriber's home provided the current to allow conversation. Magneto systems were in use in some small towns in the U.S. as late as the 1980s.
In large cities, such as New York City, with hundreds of central offices, it took many years to convert the whole city to dial service. To help automate service to manual offices during the transition to dial service, a special type of switchboard, which would display the number dialed by the customer, was used. For instance, if a customer in the MUrray Hill exchange picked up the phone and dialed a number in the CIty Island exchange, the customer would never need to know the destination number was in a manual exchange. Dialing that number would connect to the CIty Island exchange inward operator, who would see the number displayed on the switchboard, and plug into the lina.
Automatic telephone exchanges These came into existence in the early 1900s. They were designed to replace the need for human telephone operators. Before the exchanges became automated, operators had to complete the connections required for a telephone call. Almost everywhere, operators have been replaced by computerized exchanges. A telephone operator at work on a private switchboard A telephone operator is either a person who provides assistance to a telephone caller, usually in the placing of operator assisted telephone calls such as calls from a pay phone, collect calls (called reversed-charge calls in the UK), calls which...
A telephone call is a connection over a telephone network between the calling party and the called party. ...
The local exchange automatically senses an off hook (tip) telephone condition, provides dial tone to that phone, receives the pulses or DTMF tones generated by the phone, and then completes a connection to the called phone within the same exchange or to another distant exchange. The telephone or phone (Greek: tele = far away and phone = voice) is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. ...
A dial tone is a telephony signal used to indicate that the telephone exchange is working and ready to accept a call. ...
Dual-tone multi-frequency (DTMF), also known as Touch Tone® is used for telephone signaling over the line in the voice frequency band to the call switching center. ...
The exchange then maintains the connection until a party hangs up, and the connection is disconnected. Additional features, such as billing equipment, may also be incorporated into the exchange.
Early exchanges used motors, shaft drives, rotating switches and relays. Some types of automatic exchanges were Strowger (also known as Step-By-Step), All Relay, X-Y, Panel and Crossbar. Relay as used in cars A relay is an electromechanical switch that uses an electromagnet to open or close one or many sets of contacts. ...
Almon Brown Strowger (1839 - May 26, 1902) gave his name to the electromechanical telephone exchange technology that his invention and patent inspired. ...
The Panel telephone switch was an early type of automatic telephone exchange, first put into service in the 1920s. ...
A crossbar switch is an electromechanical device for switching telephone calls. ...
Telephone switches A telephone switch is the brains of an exchange. It is a device for routing calls from one telephone to another, generally as part of the public switched telephone network. They work by connecting two or more digital virtual circuits together, according to a dialed telephone number. Calls are setup between switches using the Signalling System 7 protocol, or one of its variants. This article discusses routing in computer networks. ...
The telephone or phone (Greek: tele = far away and phone = voice) is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. ...
The public switched telephone network (PSTN) is the concentration of the worlds public circuit-switched telephone networks, in much the same way that the Internet is the concentration of the worlds public IP-based packet-switched networks. ...
A telephone number is a string of decimal digits that uniquely indicates the network termination point. ...
Signalling System #7 (SS7)karunagaran karunagarn is a set of telephony signalling protocols which are used to set up the vast majority of the worlds PSTN telephone calls. ...
Digital switches encode the speech going on, in extremely minute time slices — many per second. At each time slice, a digital representation of the tone is made. The digits are then sent to the receiving end of the line, where the reverse process occurs, to produce the sound for the receiving phone. In other words, when you use a telephone, you are generally having your voice "encoded" and then reconstructed for the person on the other end. Your voice is very slightly delayed in the process (probably by only a small fraction of one second) — it is not "live", it is reconstructed — delayed only minutely. (See below for more info.)
Individual local loop telephone lines are connected to a remote concentrator. In many cases, the concentrator is co-located in the same building as the switch. The interface between concentrators and telephone switches has been standardised by ETSI as the V5 protocol. In telecommunications, the local loop is the wiring between the central office (telephone exchange in British English) and the customers premises demarcation point. ...
In modern telephony a remote concentrator is the lowest level in the telephone switch hierarchy. ...
The European Telecommunications Standards Institute (ETSI) is a standardization organization of the telecommunications industry (equipment makers and network operators) in Europe, with worldwide projection. ...
V5 is a set of protocols defined by ETSI by which a multiplexer in the access network of the PSTN can communicate with a telephone exchange. ...
Some telephone switches do not have concentrators directly connected to them, but rather are used to connect calls between other telephone switches. Usually a complex machine (or series of them) in a central exchange building, these are referred to as "carrier-level" switches or tandems.
Some telephone exchange buildings in small towns now house only remote switches, and are homed "parent" switch, usually several kilometres away. The remote switch is dependent on the parent switch for routing and number plan information. Unlike a digital loop carrier, a remote switch can route calls between local phones itself, without using trunks to the parent switch. The local loop is the physical connection between the main distribution frame in the users premises to the telecommunications network provider. ...
Telephone switches are usually owned and operated by a telephone service provider or "carrier" and located in their premises, but sometimes individual businesses or private commercial buildings will house their own switch, called a PBX, or Private Branch Exchange. PBX redirects here. ...
Telephone Shareing - Intercom Pages another popular Voip: Free Global Communications with Voip Telephony. Worlds first community based [free call] telephone & Voice over IP network softphone.
In computing, a soft phone is software that simulates a real phone and runs on a general purpose computer, rather than a dedicated device. ...
The switch's place in the system Telephone switches are a small part of a large network. The majority of work and expense of the phone system is the wiring outside the central office, or the "Outside Plant".
Some companies use "pair gain" devices to provide telephone service to subscribers. These devices are used to provide service where existing copper facilities have been exhausted or by siting in a neighborhood, can reduce the length of copper pairs, enabling digital services such as ISDN or DSL. Pair gain or digital loop carriers (DLCs) are located outside the central office, usually in a large neighborhood distant from the CO. ISDN is also short for isosorbide dinitrate Integrated Services Digital Network (ISDN) is a type of circuit switched telephone network system, designed to allow digital (as opposed to analog) transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds, than available with analog...
A typical DSL Modem Digital Subscriber Line, or DSL, is a family of technologies that provide digital data transmission over the wires used in the last mile of a local telephone network. ...
The local loop is the physical connection between the main distribution frame in the users premises to the telecommunications network provider. ...
DLCs are often referred to as Subscriber Loop Carriers (SLCs), after Lucent's proprietary name for their pair gain products. Early SLC systems (SLC-1) used an analog carrier for transport between the remote site and the central office. Later systems (SLC-96, SLC-5) and other vendors' DLC products contain line cards that convert the analog signal to a digital signal (usually PCM). This digital signal can then be transported over copper, fiber, or other transport medium to the central office. Other components include ringing generators to provide ringing current and battery backups. In 1996, AT&T spun off its Systems and Technology units, along with the famous Bell Laboratories, to form a new company named Lucent Technologies (NYSE: LU). ...
Telecomunications The Line Card is an electronic printed circuit board in an access network element of a telecommunication network. ...
PCM is an initialism which can have different meanings: Phase Change Material Pulse-code modulation, a way to digitally encode signals representing sound and their video counterparts Potential Cancer Marker Communist Party of Mexico Plug Compatible Manufacturer Power-train control module, a computer in a car which controls the car...
DLCs can be configured as universal (UDLCs) or integrated (IDLCS). Universal DLCs have two terminals, a central office terminal (COT) and a remote terminal (RT), that function similarly. Both terminals interface with analog signals, convert to digital signals, and transport to the other side where the reverse is performed. Sometimes, the transport is handled by separate equipment. In an Integrated DLC, the COT is eliminated. Instead, the RT is connected digitally to equipment in the telephone switch. This reduces the total amount of equipment required. Several standards cover DLCs, including Telcordia's TR/GR-008 & TR/GR-303. ...
Switches are used in both local central offices and in long distance centers.
Switch design Long distance switches may use a slower, more efficient switch-allocation algorithm than central offices, because they have near 100% utilization of their input and output channels. Central offices have more than 90% of their channel capacity unused.
While traditionally, telephone switches connected physical circuits (e.g., wire pairs), modern telephone switches use a combination of space- and time-division switching. In other words, each voice channel is represented by a time slot (say 1 or 2) on a physical wire pair (A or B). In order to connect two voice channels (say A1 and B2) together, the telephone switch interchanges the information between A1 and B2. It switches both the time slot and physical connection. To do this, it exchanges data between the time slots and connections 8000 times per second, under control of digital logic that cycles through electronic lists of the current connections. Using both types of switching makes a modern switch far smaller than either a space or time switch could be by itself. The term multiplexer has uses in several fields of application: Electronics In electronics, a multiplexer or mux is a device that combines several electrical signals into a single signal. ...
Time-division multiplexing (TDM) is a type of digital multiplexing in which two or more apparently simultaneous channels are derived from a given frequency spectrum, i. ...
The structure of a switch is an odd number of layers of smaller, simpler subswitches. Each layer is interconnected by a web of wires that goes from each subswitch, to a set of the next layer of subswitches. In most designs, a physical (space) switching layer alternates with a time switching layer. The layers are symmetric, because in a telephone system callers can also be callees. A substitute for a 16x16 crossbar switch made from 12 4x4 crossbar switches. ...
A time-division subswitch reads a complete cycle of time slots into a memory, and then writes it out in a different order, also under control of a cyclic computer memory. This causes some delay in the signal.
A space-division subswitch switches electrical paths, often using some variant of a nonblocking minimal spanning switch, or a crossover switch. A substitute for a 16x16 crossbar switch made from 12 4x4 crossbar switches. ...
Crossover Switches are complex array matrixes to switch any one input path to any one(or more) output path(s). ...
Switch control algorithms
Fully-connected mesh network One way is to have enough switching fabric to assure that the pairwise allocation will always succeed by building a fully-connected mesh network. This is the method usually used in central office switches, which have low utilization of their resources. A network topology is the pattern of links connecting pairs of nodes of a network. ...
Clos's nonblocking switch algorithm The scarce resources in a telephone switch are the connections between layers of subswitches. The control logic has to allocate these connections, and most switches do so in a way that is fault tolerant. See nonblocking minimal spanning switch for a discussion of Charles Clos's algorithm, used in many telephone switches, and arguably one of the most important algorithms in modern industry. Fault-tolerance or graceful degradation is the property of a system that continues operating properly in the event of failure of some of its parts. ...
A substitute for a 16x16 crossbar switch made from 12 4x4 crossbar switches. ...
Fault tolerance Composite switches are inherently fault-tolerant. If a subswitch fails, the controlling computer can sense it during a periodic test. The computer marks all the connections to the subswitch as "in use". This prevents new calls, and does not interrupt old calls that remain working. As calls are ended, the subswitch then becomes unused. Some time later, a technician can replace the circuit board. The next test succeeds, the connections to the repaired subswitch are marked "not in use", and the switch returns to full operation.
To prevent frustration with unsensed failures, all the connections between layers in the switch are allocated using first-in-first-out lists. That way, when a disgusted customer hangs up and redials, they will get a different set of connections and subswitches. A last-in-first-out allocation of connections might cause a continuing string of very frustrating failures.
See also:
- DSL
- ISDN
- PDH
- PBX Private Branch Exchange or business-level switch
The definition below is very technical, and a lot of it appears to be US-specific: A typical DSL Modem Digital Subscriber Line, or DSL, is a family of technologies that provide digital data transmission over the wires used in the last mile of a local telephone network. ...
Integrated Services Digital Network (ISDN) is a type of circuit switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds than available with analog systems. ...
The Plesiochronous Digital Hierarchy (PDH) is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems. ...
PBX redirects here. ...
In telecommunication, a central office (C.O.) is a common carrier switching center in which trunks and local loops are terminated and switched. BlackBerry 7100t Telecommunication refers to communication over long distances. ...
A common carrier is an organization that transports a product or service using its facilities, or those of other carriers, and offers its services to the general public. ...
A switching center is a node in a telecommunications Circuit switching network which is connected to either another switching center and/or to end user devices. ...
In telecommunications, the local loop is the wiring between the central office (telephone exchange in British English) and the customers premises demarcation point. ...
Note: In the DOD, "common carrier" is called "commercial carrier." Synonyms exchange, local central office, local exchange, local office, switching center (except in DOD DSN [formerly AUTOVON] usage), switching exchange, telephone exchange. Deprecated synonym switch. It has been suggested that switching be merged into this article or section. ...
Source: from Federal Standard 1037C Federal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U.S. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ...
Usage Many of the terms in this article have conflicting UK and US usages. - central office originally referred to the switching equipment itself. Now it is used generally for the building housing switching and related equipment.
- telephone exchange means an exchange building in the UK, and is also the UK name for a telephone switch, and also has a technical meaning in U.S. telecoms.
- telephone switch is the U.S. term, but is in increasing use in technical UK telecoms usage, to make the CO/switch/concentrator distinction clear
See also This is intended to be a list of the more common central office (telephone company operated) phone switches. ...
In telecommunications, a pair-gain system is a network amplifier system used to increase the strength of signals on paired wires installed to reach distances up to about five miles (8 km). ...
This article needs to be wikified. ...
A softswitch is a central device in a telephone network which connects calls from one phone line to another, entirely by means of software running on a computer system. ...
External links |
Feeds |
Contact