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Telephone Exchange
A TELEPHONE EXCHANGE is a telecommunications system used in the public switched telephone network or in large enterprises. An exchange consists of electronic components and in older systems also human operators that interconnect (switch) 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 (CO), a Bell System
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. Central office locations may also be identified in North America as wire centers, designating a facility from which a telephone obtains dial tone
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Stepping Switch
In electrical controls, a STEPPING SWITCH or stepping relay , also known as a UNISELECTOR, is an electromechanical device that switches an input signal path to one of several possible output paths, directed by a train of electrical pulses. The major use of stepping switches was in early automatic telephone exchanges to route telephone calls . Later, they were often used in such equipment as industrial control systems. They were used in Japanese cypher machines during World War 2 , known to the Americans as CORAL , JADE , and PURPLE . Code breakers at Bletchley Park employed uniselectors driven by a continuously rotating motor rather than a series of pulses in the Bombe
Bombe
machines to cryptanalyse the German Enigma ciphers. In a uniselector, the stepping switch steps only on one axis, although there are often several sets of contacts in parallel
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Kansas City, Missouri
KANSAS CITY is the largest city in Missouri
Missouri
, United States. According to the U.S. Census Bureau, the city had an estimated population of 481,420 in 2016, making it the 37th largest city by population in the United States
United States
. It is the central city of the Kansas City
City
metropolitan area , which straddles the Kansas
Kansas
–Missouri border. Kansas
Kansas
City
City
was founded in the 1830s as a Missouri
Missouri
River port at its confluence with the Kansas
Kansas
River coming in from the west. On June 1, 1850 the town of Kansas
Kansas
was incorporated; shortly after came the establishment of the Kansas
Kansas
Territory
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Telephone Dial
A ROTARY DIAL is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing . It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange . On the rotary dial, the digits are arranged in a circular layout so that a finger wheel may be rotated with one finger from the position of each digit to a fixed stop position, implemented by the finger stop, which is a mechanical barrier to prevent further rotation. When released at the finger stop, the wheel returns to its home position by spring action at a speed regulated by a governor device . During this return rotation, the dial interrupts the direct electrical current of the telephone line (local loop ) a specific number of times for each digit and thereby generates electrical pulses which the telephone exchange decodes into each dialed digit
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Panel Switch
The PANEL MACHINE SWITCHING SYSTEM is an early type of automatic telephone exchange for urban service, introduced in the Bell System
Bell System
in the 1920s. It was developed by Western Electric Labs, the forerunner of Bell Labs
Bell Labs
, in the U.S., in parallel with the Rotary system at International Western Electric in Belgium before World War I, which was used in Europe. Both systems had many features in common. The first Panel-type exchanges were placed in service in Newark, New Jersey , on January 16, 1915 at the Mulberry central office, and on June 12 in the Waverly central office. These system were semi-mechanical systems using telephones at customer stations without a dial. Operators answered calls and keyed the station number into the panel switch
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Crossbar Switch
In electronics , 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 semiconductor chips. The cross-point switch is one of the principal switch architectures, together with a rotary switch , memory switch, and a crossover switch
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Ringdown
In telephony , RINGDOWN is a method of signaling an operator in which telephone ringing current is sent over the line to operate a lamp or cause the operation of a self-locking relay known as a drop. Ringdown
Ringdown
is used in manual operation, as distinguished from automatic signaling by dialing a number. The signal consists of a continuous or pulsed alternating current (AC) signal transmitted over the line. It may be used with or without a telephone switchboard . The term originated in magneto telephone signaling in which cranking the magneto generator, either integrated into the telephone set or housed in a connected ringer box, would not only ring its bell but also cause a drop to fall down at the telephone exchange switchboard, marked with the number of the line to which the magneto telephone instrument was connected
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Trunking
In telecommunications , TRUNKING is a method for a system to provide network access to many clients by sharing a set of lines or frequencies instead of providing them individually. This is analogous to the structure of a tree with one trunk and many branches. Examples of this include telephone systems and the two-way radios commonly used by police agencies. More recently port trunking has been applied in computer networking as well. A TRUNK is a single transmission channel between two points, each point being either the switching center or the node
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Telephone Line
A TELEPHONE LINE or TELEPHONE CIRCUIT (or just LINE or CIRCUIT within the industry ) is a single-user circuit on a telephone communication system. This is the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually also implies a single telephone number for billing purposes reserved for that user. Telephone
Telephone
lines are used to deliver landline telephone service and Digital subscriber line (DSL) phone cable service to the premises. Telephone
Telephone
overhead lines are connected to the public switched telephone network . UNITED STATESIn 1878, the Bell Telephone
Telephone
Company began to use two-wire circuits (called the local loop ) from each user's telephone to end offices which performed any necessary electrical switching to allow voice signals to be transmitted to more distant telephones
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Cord Circuit
In telecommunication , a CORD CIRCUIT is a switchboard circuit in which a plug-terminated cord is used to establish connections manually between user lines or between trunks and user lines. A number of cord circuits are furnished as part of the switchboard position equipment. The cords may be referred to as front cord and rear cord or trunk cord and station cord. In modern cordless switchboards, the cord-circuit function is switch operated and may be programmable . In early and middle 20th century telephone exchanges this task was done by a supervisory relay set known variously as junctor circuit or district junctor . Later designs made it a function of the trunk circuit or absorbed it into software
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Calling Party
The CALLING PARTY (in some contexts called the "A-Number") is a person who (or device that) initiates a telephone call . The person who, or device that, receives a telephone call is the called party . In some countries, it is common etiquette for a call originator to identify himself first instead of the receiver, when the connection is established. Modems and fax machines use different tones when originating or answering a connection, which may be a source of problems for the user. SEE ALSO * Calling-party camp-on This article related to telephony is a stub . You can help by expanding it
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DTMF
DUAL-TONE MULTI-FREQUENCY SIGNALING (DTMF) is an in-band telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers . DTMF was first developed in the Bell System in the United States, and became known under the trademark TOUCH-TONE for use in push-button telephones supplied to telephone customers, starting in 1963. DTMF is standardized as ITU-T Recommendation Q.23. It is also known in the UK as MF4. The Touch-Tone system using a telephone keypad gradually replaced the use of rotary dial and has become the industry standard for landline and mobile service. Other multi-frequency systems are used for internal signaling within the telephone network
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Off-hook
In telephony , the term OFF-HOOK has the following meanings: Off hook telephone. * The condition that exists when a telephone or other user instrument is in use, i.e., during dialing or communicating. * A general description of one of two possible signaling states at an interface between telecommunications systems, such as tone or no tone and ground connection versus battery connection. Note that if off-hook pertains to one state, on-hook pertains to the other. * The active state (i.e., a closed loop (short circuit between the wires) of a subscriber line or PBX user loop) * An operating state of a communications link in which data transmission is enabled either for (a) voice or data communications or (b) network signaling . On an ordinary two-wire telephone line, off-hook status is communicated to the telephone exchange by a resistance short across the pair
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Rotary Dial
A ROTARY DIAL is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing . It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange . On the rotary dial, the digits are arranged in a circular layout so that a finger wheel may be rotated with one finger from the position of each digit to a fixed stop position, implemented by the finger stop, which is a mechanical barrier to prevent further rotation. When released at the finger stop, the wheel returns to its home position by spring action at a speed regulated by a governor device . During this return rotation, the dial interrupts the direct electrical current of the telephone line (local loop ) a specific number of times for each digit and thereby generates electrical pulses which the telephone exchange decodes into each dialed digit
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Common Battery
In telecommunication , a COMMON BATTERY is a single electrical power source used to energize more than one circuit , electronic component , equipment, or system . A common battery is usually a string of electrolytic cells and is usually centrally located to the equipment that it serves. In many telecommunications applications, the common battery is at a nominal −48 VDC. A central office common battery in the battery room supplies power to operate all directly connected instruments. Common battery may include one or more power conversion devices to transform commercial power to direct current, with a rechargeable battery floating across the output. Common battery operation largely replaced local batteries in each telephone in the early 20th century
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