157:
149:
1477:
883:
33:
992:
1421:(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 8,000 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.
544:
1513:
45:
828:
1215:
599:
1300:
778:, a handshake took place to prevent both switches from colliding by dialing calls on the same trunk at the same time. By changing the state of these leads from ground to −48 volts, the switches stepped through a handshake protocol. Using DC voltage changes, the local switch would send a signal to get ready for a call and the remote switch would reply with an acknowledgment (a wink) to go ahead with dial pulsing. This was done with relay logic and discrete electronics.
1292:
3096:
540:, and connected the call by plugging a cord into the outgoing circuit and ringing the destination station. For example, if a dial customer calling from TAylor 4725 dialed a number served by a manual exchange, e.g., ADams 1383-W, the call was completed, from the subscriber's perspective, exactly as a call to LEnnox 5813, in an automated exchange. The party line letters W, R, J, and M were only used in manual exchanges with jack-per-line party lines.
764:. In one case, seven digit numbers were preceded by a digit 1 or 2 to differentiate between two area codes or office codes, (a two-digit-per-call savings). This improved revenue per trunk and reduced the number of digit receivers needed in a switch. Every task in electromechanical switches was done in big metallic pieces of hardware. Every fractional second cut off of call set up time meant fewer racks of equipment to handle call traffic.
478:
1005:
3106:
1323:(MDF). A component of the MDF is protection: fuses or other devices that protect the switch from lightning, shorts with electric power lines, or other foreign voltages. In a typical telephone company, a large database tracks information about each subscriber pair and the status of each jumper. Before computerization of Bell System records in the 1980s, this information was handwritten in pencil in accounting ledger books.
771:, SF signaling, and robbed-bit signaling. In physical (not carrier) E and M trunk circuits, trunks were four wire. Fifty trunks would require a hundred pair cable between switches, for example. Conductors in one common circuit configuration were named tip, ring, ear (E) and mouth (M). Tip and ring were the voice-carrying pair, and named after the tip and ring on the three conductor cords on the manual operator's console.
3085:
3116:
139:
1245:), to produce the sound for the receiving phone. In other words, when someone uses a telephone, the speaker's voice is "encoded" using PCM for switching then reconstructed for the person on the other end. The speaker's voice is delayed in the process by a small fraction of one second — it is not "live", it is reconstructed — delayed only minutely.
304:
would automatically begin as soon as the operator inserted the ringing cord into the called party's jack. The operator would be disconnected from the circuit, allowing them to handle another call, while the caller heard an audible ringback signal, so that that operator would not have to periodically report that they was continuing to ring the line.
165:
In the era of the electrical telegraph, its principal users were post offices, railway stations, the more important governmental centers (ministries), stock exchanges, very few nationally distributed newspapers, the largest internationally important corporations, and wealthy individuals. Despite the
890:
Electromechanical switching systems required sources of electricity in form of direct current (DC), as well as alternating ring current (AC), which were generated on-site with mechanical generators. In addition, telephone switches required adjustment of many mechanical parts. Unlike modern switches,
738:
In Bell System trunks, it was common to use 20 pulse-per-second between crossbar switches and crossbar tandems. This was twice the rate of
Western Electric/Bell System telephone dials. Using the faster pulsing rate made trunk utilization more efficient because the switch spent half as long listening
569:
telephones, which had a crank for the signaling generator. To alert the operator, or another subscriber on the same line, the subscriber turned the crank to generate ringing current. The switchboard responded by interrupting the circuit, which dropped a metal tab above the subscriber's line jack and
1496:
which interconnects them increases, potential disruption caused by destruction of one local office will only be magnified. Multiple fibre connections can be used to provide redundancy to voice and data connections between switching centres, but careful network design is required to avoid situations
1456:
Composite switches are inherently fault-tolerant. If a subswitch fails, the controlling computer can sense the failure during a periodic test. The computer marks all the connections to the subswitch as "in use". This prevents new calls, and does not interrupt established calls. As established calls
118:
code (NPA code or area code), making central office codes distinctive within each numbering plan area. These codes served as prefixes in subscriber telephone numbers. The mid-20th century saw similar organizational efforts in telephone networks globally, propelled by the advent of international and
1428:
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 some designs, a physical (space) switching layer alternates with a time switching layer. The layers are symmetric,
1096:
is the most widely used digital switching platform in the world and can be found throughout Europe and in most countries around the world. It is also very popular in mobile applications. This highly modular system was developed in Sweden in the 1970s as a replacement for the very popular range of
970:
series and several other designs were similar. Ericsson also developed a fully computerized version of their ARF crossbar exchange called ARE. These used a crossbar switching matrix with a fully computerized control system and provided a wide range of advanced services. Local versions were called
311:
method, the originating operator called another intermediate operator who would call the called subscriber, or passed it on to another intermediate operator. This chain of intermediate operators could complete the call only if intermediate trunk lines were available between all the centers at the
303:
Early manual switchboards required the operator to operate listening keys and ringing keys, but by the late 1910s and 1920s, advances in switchboard technology led to features which allowed the call to be automatically answered immediately as the operator inserted the answering cord, and ringing
497:
to connect the call to a requested number. Provided that the number is in the same central office, and located on the operator's switchboard, the operator connects the call by plugging the ringing cord into the jack corresponding to the called customer's line. If the called party's line is on a
174:
A telephone exchange is a telephone system for a small geographic area that provides the switching (interconnection) of subscriber lines for calls made between them. Telephone exchanges replaced small telephone systems that connected its users with direct lines between each and every subscriber
1127:
Alcatel developed the E10 system in France during the late 1960s and 1970s. This widely used family of digital switches was one of the earliest TDM switches to be widely used in public networks. Subscribers were first connected to E10A switches in France in 1972. This system is used in France,
516:
When a subscriber's phone is off-hook, it presents an electrical resistance across the line which causes current to flow through the telephone and wires to the central office. In a manually operated switchboard, this current flowed through a relay coil, and actuated a buzzer or a lamp on the
1061:
as part of the ESSEX project while the first true digital exchange to be combined with digital transmission systems was designed by LCT (Laboratoire
Central de Telecommunications) in Paris. The first digital switch to be placed into a public network in England was the Empress Exchange in
781:
These voltage changes on the trunk circuit would cause pops or clicks that were audible to the subscriber as the electrical handshaking stepped through its protocol. Another handshake, to start timing for billing purposes, caused a second set of clunks when the called party answered.
815:
were translated to changes in contact states (opens and closures) by electronics in the channel bank hardware. This allowed direct current E and M signaling, or dial pulses, to be sent between electromechanical switches over a digital carrier which did not have DC continuity.
662:
service. In manual service, the operator knows where a call is originating by the light on the switchboard jack field. Before ANI, long-distance calls were placed into an operator queue and the operator asked the calling party's number and recorded it on a paper toll ticket.
331:, each pair of digits caused the shaft of the central contact "hand" of the stepping switch to first step (ratchet) up one level for each pulse in the first digit and then to swing horizontally in a contact row with one small rotation for each pulse in the next digit.
327:, a device which led to the automation of telephone circuit switching. While there were many extensions and adaptations of this initial patent, the one best known consists of 10 levels or banks, each having 10 contacts arranged in a semicircle. When used with a rotary
869:
Bell System installations typically had alarm bells, gongs, or chimes to announce alarms calling attention to a failed switch element. A trouble reporting card system was connected to switch common control elements. These trouble reporting systems punctured cardboard
1316:, which is the wiring outside the central office. While many subscribers were served with party-lines in the middle of the 20th century, it was the goal that each subscriber telephone station were connected to an individual pair of wires from the switching system.
904:
Delinquent subscribers had their service temporarily denied (TDed). This was effected by plugging a tool into the subscriber's office equipment on
Crossbar systems or line group in step-by-step switches. The subscriber could receive calls but could not dial out.
170:
and structure of the contemporary telegraph, as prior to the invention of the telephone exchange switchboard, early telephones were hardwired to and communicated with only a single other telephone (such as from an individual's home to the person's business).
1330:" 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
974:
These systems could use the old electromechanical signaling methods inherited from crossbar and step-by-step switches. They also introduced a new form of data communications: two 1ESS exchanges could communicate with one another using a data link called
436:
originally was a primary exchange in a city with other exchanges service parts of the area. The term became to mean any switching system including its facilities and operators. It is also used generally for the building that houses switching and related
126:(PBX), which connects to the public switched telephone network. A PBX serves an organization's telephones and any private leased line circuits, typically situated in large office spaces or organizational campuses. Smaller setups might use a PBX or
1360:
s 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.
1139:
which when it bought ITT's
European operations. The S12 system and E10 systems were merged into a single platform in the 1990s. The S12 system is used in Germany, Italy, Australia, Belgium, China, India, and many other countries around the
920:) would be connected to a call just long enough to collect the subscriber's dialed digits. Crossbar architecture was more flexible than step offices. Later crossbar systems had punch-card-based trouble reporting systems. By the 1970s,
498:
different switchboard in the same office, or in a different central office, the operator plugs into the trunk for the destination switchboard or office and asks the operator answering (known as the "B" operator) to connect the call.
160:
1903 manual switch for four subscriber lines (top) with four cross-bar talking circuits (horizontal), and one bar to connect the operator (T). The lowest cross-bar connects idle stations to ground to enable the signaling indicators
509:. In common-battery systems, the pair of wires from a subscriber's telephone to the exchange carry 48V (nominal) DC potential from the telephone company end across the conductors. The telephone presents an open circuit when it is
340:. If one of up to a hundred subscriber lines (two hundred lines in later linefinders) had the receiver lifted "off hook", a linefinder connected the subscriber's line to a free first selector, which returned the subscriber a
899:
s were plugged into electromechanical switch elements upon failure and during repairs. A make-busy identified the part being worked on as in-use, causing the switching logic to route around it. A similar tool was called a
1268:
Some telephone switches do not have concentrators directly connected to them, but rather are used to connect calls between other telephone switches. These complex machines are referred to as "carrier-level" switches or
908:
Strowger-based, step-by-step offices in the Bell System required continuous maintenance, such as cleaning. Indicator lights on equipment bays alerted staff to conditions such as blown fuses (usually white lamps) or a
894:
The design and maintenance procedures of all systems involved methods to avoid that subscribers experienced undue changes in the quality of the service or that they noticed failures. A variety of tools referred to as
574:
batteries, normally two large N°. 6 cells in the subscriber's telephone, provided the direct current for the transmitter. Such magneto systems were in use in the US as late as 1983, as in the small town, Bryant Pond,
971:
ARE11 while tandem versions were known as ARE13. They were used in
Scandinavia, Australia, Ireland and many other countries in the late 1970s and into the 1980s when they were replaced with digital technology.
793:. The most common form of this used a steady 2,600 Hz tone to identify a trunk as idle. Trunk circuitry hearing a 2,600 Hz tone for a certain duration would go idle. (The duration requirement reduced
1436:
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.
625:. Automation replaced human operators with electromechanical systems, and telephones were equipped with a dial by which a caller transmitted the destination telephone number to the automatic switching system.
1264:
protocol. Concentrators are used because most telephones are idle most of the day, hence the traffic from hundreds or thousands of them may be concentrated into only tens or hundreds of shared connections.
846:
528:
format (two-letter exchange name and either four or five digits), it was possible to dial a number located in a manual exchange and be connected without requesting operator assistance. The policy of the
344:
to show that it was ready to receive dialled digits. The subscriber's dial pulsed at about 10 pulses per second, although the speed depended on the standard of the particular telephone administration.
355:
technology. These exchange designs promised faster switching and would accept inter-switch pulses faster than the
Strowger's typical 10 pps—typically about 20 pps. At a later date many also accepted
562:
for an automated office with two capital letters, a manual office, having listings such as
Hillside 834 or East 23, was recognizable by the format in which the second letter was not capitalized.
1057:
First concepts of digital switching and transmission were developed by various labs in the United States and in Europe starting in the 1930s. The first prototype digital switch was developed by
362:
A transitional technology (from pulse to DTMF) had converters to convert DTMF to pulse, to feed to older
Strowger, panel, or crossbar switches. This technology was used as late as mid-2002.
300:
circuit to connect to another operator in another bank of boards or at a remote central office. In 1918, the average time to complete the connection for a long-distance call was 15 minutes.
712:
electromechanical switches in the United States originally communicated with one another over trunks using a variety of DC voltages and signaling tones, replaced today by digital signals.
370:
Many terms used in telecommunication technology differ in meaning and usage among the various
English speaking regions. For the purpose of this article the following definitions are made:
312:
same time. In 1943 when military calls had priority, a cross-country US call might take as long as 2 hours to request and schedule in cities that used manual switchboards for toll calls.
757:
standard. Similar schemes were used in the
Americas and in some European countries including Spain. Digit strings between switches were often abbreviated to further improve utilization.
844:
811:
digital transmission systems, bits within the T-1 data stream were used to transmit supervision. By careful design, the appropriated bits did not change voice quality appreciably.
95:
equipment for one or several telephone exchanges, each catering to a specific geographical region. This region is sometimes known as the exchange area. In North America, the term
945:-switched metallic paths under digital control. Equipment testing, phone numbers reassignments, circuit lockouts and similar tasks were accomplished by data entry on a terminal.
1387:
or subscriber switches, which manage connections from subscriber telephones. Since the 1990s, hybrid Class 4/5 switching systems that serve both functions have become common.
1256:. In many cases, the concentrator is co-located in the same building as the switch. The interface between remote concentrators and telephone switches has been standardised by
107:
for business and billing purposes, which in large cities, might encompass clusters of central offices to specify geographic locations for distance measurement calculations.
845:
505:
service, meaning that the central office provided power to the subscriber telephone circuits for operation of the transmitter, as well as for automatic signaling with
292:) into the subscriber's jack and switched their headset into the circuit to ask, "Number, please?" For a local call, the operator inserted the front cord of the pair (
590:
sequence, such as two long rings followed by one short ring. Everyone on the line could hear the signals, and could pick up and monitor other people's conversations.
640:
tones generated by the telephone are processed and a connection is established to the destination telephone within the same exchange or to another distant exchange.
72:(PSTN) or large enterprise telecommunications systems. It facilitates the interconnection of telephone subscriber lines or digital system virtual circuits, enabling
1840:
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fact that telephone devices existed before the invention of the telephone exchange, their success and economical operation would have been impossible on the same
1464:(queues). As a result, if a connection is faulty or noisy and the customer hangs up and redials, they will get a different set of connections and subswitches. A
175:
station. Exchanges made telephony an available and comfortable technology for everyday use and it gave the impetus for the creation of a new industrial sector.
1988:
1603:
2360:
1368:, the COT is eliminated. Instead, the RT is connected digitally to equipment in the telephone switch. This reduces the total amount of equipment required.
1284:
switches, and are homed upon a "parent" switch, usually several kilometres away. The remote switch is dependent on the parent switch for routing. Unlike a
1241:
representation of the sound is made. The digital PCM signals are then sent to the receiving end of the line, where the reverse process occurs using a DAC (
617:
in 1888. First used commercially in 1892, they did not gain widespread use until the first decade of the 20th century. They eliminated the need for human
533:
stated that customers in large cities should not need to be concerned with the type of office, whether they were calling a manual or an automatic office.
1312:
Telephone switches are a small component of a large network. A major part, in terms of expense, maintenance, and logistics of the telephone system is
1410:, because they have near 100% utilization of their input and output channels. Central offices have more than 90% of their channel capacity unused.
1977:
Connected to a switch, an off-hook condition operates a relay to connect the line to a dial tone generator and a device to collect dialed digits.
891:
a circuit connecting a dialed call through an electromechanical switch had DC continuity within the local exchange area via metallic conductors.
156:
1390:
Another element of the telephone network is time and timing. Switching, transmission and billing equipment may be slaved to very high accuracy
536:
When a subscriber dialed the number of a manual station, an operator at the destination office answered the call after seeing the number on an
221:. The switchboard was built from "carriage bolts, handles from teapot lids and bustle wire" and could handle two simultaneous conversations.
3068:
3040:
3035:
2060:
913:(stuck off-hook condition, usually green indicators). Step offices were more susceptible to single-point failures than newer technologies.
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1732:
586:, anywhere from two to ten or more subscribers sharing a single line. When calling a party, the operator used code ringing, a distinctive
1632:
1827:
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which synchronize time events to very close intervals. Time-standards equipment may include Rubidium- or Caesium-based standards and a
727:
and a manual switchboard. Probably the most common form of communicating dialed digits between electromechanical switches was sending
1810:
1753:
745:
was the last of the pre-digital methods. It used a different set of tones sent in pairs like DTMF. Dialing was preceded by a special
1191:
GTD-5 EAX developed by GTE Automatic Electric, the GTD-5 was acquired by Lucent which became Alcatel-Lucent, which then became Nokia
1413:
Traditional telephone switches connected physical circuits (e.g., wire pairs) while modern telephone switches use a combination of
1171:
1345:(DLCs) are located outside the central office, usually in a large neighborhood distant from the CO. DLCs are often referred to as
288:
lifted the receiver, the local loop current lit a signal lamp near the jack. The operator responded by inserting the rear cord (
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itself, the honour of "first telephone exchange" has several claimants. One of the first to propose a telephone exchange was
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end, the subswitch becomes unused, and can be repaired. When the next test succeeds, the switch returns to full operation.
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Ireland, China, and many other countries. It has been through many revisions and current versions are even integrated into
237:
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296:) into the called party's local jack and started the ringing cycle. For a long-distance call, the operator plugged into a
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originally developed by the British Post Office (later BT), GEC, Plessey and STC, is a type of digital exchange used by
916:
Crossbar offices used more shared, common control circuits. For example, a digit receiver (part of an element called an
643:
The exchange maintains the connection until one of the parties hangs up. This monitoring of connection status is called
201:
in 1877. The world's first state-administered telephone exchange opened on November 12, 1877 in Friedrichsberg close to
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To prevent frustration with unsensed failures, all the connections between layers in the switch are allocated using
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Inventors and inventions Great lives from history Volume 4 of Great Lives from History: Inventors & Inventions
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277:. In front of the jack panel lay a horizontal panel containing two rows of patch cords, each pair connected to a
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A typical central office may have tens of thousands of pairs of wires that appear on terminal blocks called the
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1288:, a remote switch can route calls between local phones itself, without using trunks to the parent switch.
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at that time to indicate to the user that the exchange is ready to receive dialed digits. The pulses or
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may be used to denote a central office location, indicating a facility that provides a telephone with a
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193:. The first experimental telephone exchange was based on the ideas of Puskás, and it was built by the
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In the largest cities, it took many years to convert every office to automatic equipment, such as a
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Rural areas, as well as the smallest towns, had manual service and signaling was accomplished with
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where a main fibre and its backup both go through the same damaged central office as a potential
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Early exchanges were electromechanical systems using motors, shaft drives, rotating switches and
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1468:(stack) allocation of connections might cause a continuing string of very frustrating failures.
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Additional features, such as billing equipment, may also be incorporated into the exchange.
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1229:. Each switch typically serves 10,000–100,000+ subscribers depending on the geographic area
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is also credited with establishing an exchange in Lowell, MA. with 50 subscribers in 1878.
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had been retrofitted to nearly all step-by-step and crossbar switches in the Bell System.
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condition represents a circuit that is in use, e.g., when a telephone call is in progress.
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routes calls as instructed by a subscriber with a telephone set that does not have a dial.
32:
8:
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Long-distance switches may use a slower, more efficient switch-allocation algorithm than
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that identified central offices with a unique three-digit code, along with a three-digit
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exchanges. The first commercial roll-out of a fully digital local switching system was
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when the user removes the handset from the switchhook or cradle. The exchange provides
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managed by a receptionist, catering to the telecommunication needs of the enterprise.
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A space-division subswitch switches electrical paths, often using some variant of a
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and time-division switching. In other words, each voice channel is represented by a
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For corporate or enterprise applications, a private telephone exchange is termed a
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Manual test board in an electromechanical switching office staffed by a technician
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is a device that concentrates traffic, be it remote or co-located with the switch.
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Digital switches encode the speech going on, in 8,000 time slices per second. (A
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systems used throughout the United States of America and in many other countries.
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Later stepping switches were arranged in banks, the first stage of which was a
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797:.) Some systems used tone frequencies over 3,000 Hz, particularly on SSB
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designed and built the first commercial US telephone exchange which opened in
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inherited three of the world's most iconic digital switching systems :
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ARF, ARM, ARK and ARE used by many European networks from the 1950s onwards.
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condition represents an idle circuit, i.e. no telephone call is in progress.
265:. Each operator sat in front of a vertical panel containing banks of ¼-inch
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In the 1940s, the Bell System in the United States and Canada introduced a
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Francis S. Wagner: Hungarian Contributions to World Civilization – Page 68
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For example, one switch might send only the last four or five digits of a
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is when an exchange routes calls by interpreting subscriber-dialed digits.
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732:
709:
530:
506:
463:
means an exchange building, and is also the name for a telephone switch.
248:
236:, both of which opened under Bell patents in 1879. Belgium had its first
88:
1291:
3006:
2713:
2411:
2320:
2276:
2246:
2224:
1795:
1546:
1249:
1143:
Finally, when Alcatel and Lucent merged, the company acquired Lucent's
1029: in this section. Unsourced material may be challenged and removed.
956:
942:
861:
767:
Examples of signals communicating supervision or call progress include
728:
628:
A telephone exchange automatically senses an off-hook condition of the
524:. During this transition period, once numbers were standardized to the
456:
270:
233:
79:
The terminology used in telecommunications has evolved over time, with
1188:
and other versions are very popular with operators all over the world.
852:
Subscribers hear a different-sounding dialtone in a step-by-step call.
2991:
2456:
2271:
2038:
1614:
1327:
1058:
808:
633:
629:
347:
Exchanges based on the Strowger switch were eventually challenged by
341:
100:
49:
1004:
477:
217:
in January, 1878, and the first telephone booth was built in nearby
40:
manually connecting calls with cord pairs at a telephone switchboard
2986:
2976:
2893:
2718:
2541:
1356:
DLCs can be configured as universal (UDLCs) or integrated (IDLCs).
1225:) used by an operator to offer local and long-distance services in
1207:
1089:
1079:
571:
517:
operator's switchboard, signaling the operator to perform service.
490:
415:
308:
297:
269:(3-conductor) jacks, each of which was the local termination of a
91:. A central office typically refers to a facility that houses the
2981:
2966:
2184:
1628:
1364:
Sometimes, the transport is handled by separate equipment. In an
1222:
1181:
1163:
794:
510:
424:
241:
183:
138:
87:
often used interchangeably, the latter term originating from the
1989:"Phone System Feared Vulnerable To Wider Disruptions of Service"
1492:
for local calls. As the capacity of individual switches and the
1433:. Other designs use time-switching only, throughout the switch.
937:
gradually evolved in stages from electromechanical hybrids with
715:
Some signaling communicated dialed digits. An early form called
3011:
2971:
2293:
1350:
1226:
1219:
1185:
1177:
1063:
667:
229:
202:
198:
48:
A modern central office, equipped with voice communication and
959:, Ericsson AXE, Automatic Electric EAX-1 & EAX-2, Philips
2996:
2933:
2241:
1938:"Basic Telephones, The Switchboard (ringdown is near bottom)"
1597:
785:
A second common form of signaling for supervision was called
754:
659:
1777:
Frank Lewis Dyer: Edison His Life And Inventions. (page: 71)
1326:
To reduce the expense of outside plant, some companies use "
1276:
Some telephone exchange buildings in small towns house only
753:(ST). Variations of the Bell System MF tone scheme became a
401:
is the area served by a particular switch or central office.
2938:
1811:"Top 50: New Haven was birth place of the modern telephone"
1383:
designed for toll or switch-to-switch connections, and the
1257:
1159:
1070:
research labs. It was a tandem switch that connected three
735:'s pulsing, but sent over trunk circuits between switches.
637:
356:
119:
transoceanic telephone trunks and direct customer dialing.
2029:
patent 252,576 for the first telephone switchboard in 1881
650:
The Bell System dial service implemented a feature called
1634:
Peer to Peer: Collaboration and Sharing Over the Internet
1197:
NEAX used in Japan, New Zealand and many other countries.
1194:
967:
654:(ANI) which facilitated services like automated billing,
979:. This data link was based on CCITT 6, a predecessor to
228:
In Europe other early telephone exchanges were based in
1371:
Switches are used in both local central offices and in
983:. In European systems R2 signalling was normally used.
1910:"Stromberg-Carlson Telephone Mfg. Co. Resource Page"
1508:
1307:
257:
Later exchanges consisted of one to several hundred
1174:
for the German market is used throughout the world.
739:to digits. DTMF was not used for trunk signaling.
1973:
1971:
995:A typical satellite PABX with front cover removed
941:to the fully digital systems. Early systems used
874:with a code that logged the nature of a failure.
3132:
1085:Prominent examples of digital switches include:
602:A rural telephone exchange building in Australia
1657:
1429:because in a telephone system callers can also
1078:'s E10 system which began serving customers in
359:"touch tones" or other tone signaling systems.
1986:
1968:
1878:
1876:
1828:National Park Service "first switchboard" page
689:
2054:
1471:
700:Circuits interconnecting switches are called
670:. Some types of automatic exchanges were the
621:who completed the connections required for a
1980:
977:Common Channel Interoffice Signaling, (CCIS)
593:
3069:Global telecommunications regulation bodies
1873:
466:
3105:
2061:
2047:
1375:centers. There are two major types in the
459:are terminated and switched. In the UK, a
394:is the switching equipment of an exchange.
1808:
1480:Second Avenue exchange, NYC, site of the
1303:Map of central office locations in the US
1045:Learn how and when to remove this message
582:Many small town magneto systems featured
103:. Telecommunication carriers also define
1809:Sundqvist, By Viktoria (22 April 2018).
1475:
1298:
1290:
1237:of 8khz). At each time slice, a digital
1213:
990:
881:
597:
542:
476:
155:
147:
137:
43:
31:
1955:
1935:
1882:
1627:
948:Examples of these systems included the
14:
3133:
2068:
1841:"Early Manchester telephone exchanges"
1488:A central exchange is almost always a
1295:Map of wire center locations in the US
929:
377:is telephone service in which a human
2042:
1482:1975 New York Telephone Exchange fire
445:jargon, a central office (C.O.) is a
3115:
1754:"Welcome hunreal.com - BlueHost.com"
1027:adding citations to reliable sources
998:
877:
152:1922 diagram of 1877 Boston exchange
1442:nonblocking minimal spanning switch
1332:Integrated Services Digital Network
1252:telephone lines are connected to a
1210:in the UK public telephone network.
986:
674:or step-by-step switch, All Relay,
24:
1451:
826:
558:In contrast to the listing format
489:, the customer lifts the receiver
27:Interconnects telephones for calls
25:
3172:
3146:Telecommunications infrastructure
2022:
1917:www.strombergcarlsontelephone.com
1688:. 4 February 2011. Archived from
1377:Public switched telephone network
1308:The switch's place in the network
723:pulses to set up calls between a
189:in 1877 while he was working for
70:public switched telephone network
3114:
3104:
3095:
3094:
3083:
2704:Free-space optical communication
1788:"120 Year Telephone anniversary"
1552:Plesiochronous digital hierarchy
1511:
1401:
1184:, and now Ribbon Communications
1082:in Northwestern France in 1972.
1003:
860:Problems playing this file? See
842:
68:, is a crucial component in the
1929:
1902:
1864:
1833:
1821:
1802:
1780:
1735:from the original on 2021-04-21
1710:from the original on 2005-02-24
1593:. Verizon Enterprise Solutions.
1014:needs additional citations for
923:automatic number identification
652:automatic number identification
1771:
1746:
1721:
1696:
1678:
1651:
1637:. Addison-Wesley. p. 15.
1621:
1579:
749:(KP) signal and followed by a
696:Signaling (telecommunications)
501:Most urban exchanges provided
365:
247:In 1887 Puskás introduced the
13:
1:
2034:A Telecom Exchange Tour in NZ
1987:Andrew Pollack (1988-05-26).
1936:Calvert, J. B. (2003-09-07).
1883:Calvert, J. B. (2003-09-07).
1846:. mosi.org.uk. Archived from
1756:. Hunreal.com. Archived from
1664:. Salem Press. p. 1298.
1572:
548:
547:Montreal telephone exchange (
3090:Telecommunication portal
2871:Telecommunications equipment
1686:"TIVADAR PUSKÁS (1844–1893)"
1527:History of telecommunication
935:Electronic switching systems
799:frequency-division multiplex
441:equipment. In United States
7:
2607:Alexander Stepanovich Popov
1504:
1243:digital-to-analog converter
690:Electromechanical signaling
112:nationwide numbering system
10:
3177:
2311:Telecommunications history
1562:Automatic call distributor
1532:List of telephone switches
1472:Fire and disaster recovery
1385:Class 5 telephone switches
1381:Class 4 telephone switches
1066:which was designed by the
693:
470:
180:invention of the telephone
133:
3078:
3020:
2957:
2919:Public Switched Telephone
2879:
2843:
2800:
2741:
2731:telecommunication circuit
2692:Fiber-optic communication
2675:
2437:Francis Blake (telephone)
2384:
2232:Optical telecommunication
2076:
1609:The Sydney Morning Herald
1396:Global Positioning System
594:Early automatic exchanges
2830:Orbital angular-momentum
2267:Satellite communications
2106:Communications satellite
1658:Alvin K. Benson (2010).
1557:Telephone exchange names
1462:first-in-first-out lists
1347:Subscriber Loop Carriers
1162:originally developed by
819:
467:Manual service exchanges
453:Class 5 telephone switch
2709:Molecular communication
2532:Gardiner Greene Hubbard
2361:Undersea telegraph line
2096:Cable protection system
1618:, April 19, 1878, p. 6.
1567:Public utility building
1490:single point of failure
1336:digital subscriber line
1321:main distribution frame
774:In two-way trunks with
205:under the direction of
124:private branch exchange
2851:Communication protocol
2637:Charles Sumner Tainter
2452:Walter Houser Brattain
2397:Edwin Howard Armstrong
2205:Information revolution
1963:Federal Standard 1037C
1485:
1304:
1296:
1230:
1157:Nokia Siemens Networks
1135:Alcatel also acquired
1094:AXE telephone exchange
996:
939:stored program control
887:
831:
802:microwave radio relays
603:
555:
482:
215:New Haven, Connecticut
195:Bell Telephone Company
162:
153:
145:
53:
41:
2825:Polarization-division
2557:Narinder Singh Kapany
2522:Erna Schneider Hoover
2442:Jagadish Chandra Bose
2422:Alexander Graham Bell
2153:online video platform
1587:"General Definitions"
1479:
1426:structure of a switch
1408:local central offices
1353:proprietary product.
1343:digital loop carriers
1302:
1294:
1217:
994:
885:
830:
656:toll-free 800-numbers
619:switchboard operators
601:
546:
480:
473:Telephone switchboard
321:Kansas City, Missouri
263:switchboard operators
159:
151:
141:
76:between subscribers.
47:
35:
3161:Hungarian inventions
2667:Vladimir K. Zworykin
2627:Almon Brown Strowger
2597:Charles Grafton Page
2252:Prepaid mobile phone
2180:Electrical telegraph
1542:Limited availability
1286:digital loop carrier
1218:A digital exchange (
1023:improve this article
918:Originating Register
743:Multi-frequency (MF)
717:Panel Call Indicator
481:1924 PBX switchboard
455:in which trunks and
349:other exchange types
317:Almon Brown Strowger
207:Heinrich von Stephan
128:key telephone system
3156:Telephone exchanges
3141:Telephony equipment
2617:Johann Philipp Reis
2376:Wireless revolution
2338:The Telephone Cases
2195:Hydraulic telegraph
1798:on 6 November 2014.
1692:on 4 February 2011.
1499:common mode failure
1254:remote concentrator
1068:General Post Office
963:/A, ITT Metaconta,
955:, Northern Telecom
930:Electronic switches
706:Signalling System 7
613:, were invented by
607:Automatic exchanges
319:, an undertaker in
315:On March 10, 1891,
116:numbering plan area
18:Telephone exchanges
2815:Frequency-division
2792:Telephone exchange
2662:Charles Wheatstone
2592:Jun-ichi Nishizawa
2567:Innocenzo Manzetti
2502:Reginald Fessenden
2237:Optical telegraphy
2070:Telecommunications
1997:The New York Times
1885:"Basic Telephones"
1815:New Haven Register
1604:Private Telegraphs
1486:
1305:
1297:
1231:
997:
888:
832:
731:, equivalent to a
604:
570:sounded a buzzer.
556:
483:
461:telephone exchange
379:telephone operator
238:International Bell
163:
154:
146:
81:telephone exchange
60:, also known as a
58:telephone exchange
54:
42:
38:telephone operator
3128:
3127:
2866:Store and forward
2861:Data transmission
2775:Network switching
2726:Transmission line
2572:Guglielmo Marconi
2537:Internet pioneers
2402:Mohamed M. Atalla
2371:Whistled language
1729:"Puskás, Tivadar"
1519:Telephones portal
1466:last-in-first-out
1099:crossbar switches
1055:
1054:
1047:
878:Maintenance tasks
847:
838:Step-by-step call
776:E and M signaling
769:E and M signaling
609:, which provided
443:telecommunication
52:data capabilities
16:(Redirected from
3168:
3118:
3117:
3108:
3107:
3098:
3097:
3088:
3087:
3086:
2959:Notable networks
2949:Wireless network
2889:Cellular network
2881:Types of network
2856:Computer network
2743:Network topology
2657:Thomas A. Watson
2512:Oliver Heaviside
2497:Philo Farnsworth
2472:Daniel Davis Jr.
2447:Charles Bourseul
2407:John Logie Baird
2116:Data compression
2111:Computer network
2063:
2056:
2049:
2040:
2039:
2016:
2015:
2013:
2012:
2006:
2000:. Archived from
1993:
1984:
1978:
1975:
1966:
1959:
1953:
1952:
1950:
1949:
1940:. Archived from
1933:
1927:
1926:
1924:
1923:
1914:
1906:
1900:
1899:
1897:
1896:
1887:. Archived from
1880:
1871:
1868:
1862:
1861:
1859:
1858:
1852:
1845:
1837:
1831:
1825:
1819:
1818:
1806:
1800:
1799:
1794:. Archived from
1784:
1778:
1775:
1769:
1768:
1766:
1765:
1750:
1744:
1743:
1741:
1740:
1731:. Omikk.bme.hu.
1725:
1719:
1718:
1716:
1715:
1700:
1694:
1693:
1682:
1676:
1675:
1655:
1649:
1648:
1625:
1619:
1601:
1595:
1594:
1583:
1537:Pair gain system
1521:
1516:
1515:
1514:
1446:crossover switch
1392:10 MHz standards
1349:(SLCs), after a
1117:Western Electric
1050:
1043:
1039:
1036:
1030:
1007:
999:
987:Digital switches
950:Western Electric
911:permanent signal
849:
848:
829:
787:single-frequency
762:telephone number
577:Woodstock, Maine
553:
550:
450:switching center
392:telephone switch
244:) a year later.
62:telephone switch
21:
3176:
3175:
3171:
3170:
3169:
3167:
3166:
3165:
3131:
3130:
3129:
3124:
3084:
3082:
3074:
3016:
2953:
2875:
2839:
2796:
2745:
2737:
2678:
2671:
2577:Robert Metcalfe
2432:Tim Berners-Lee
2380:
2200:Information Age
2072:
2067:
2025:
2020:
2019:
2010:
2008:
2004:
1991:
1985:
1981:
1976:
1969:
1960:
1956:
1947:
1945:
1934:
1930:
1921:
1919:
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1622:
1602:
1598:
1591:Verizon service
1585:
1584:
1580:
1575:
1517:
1512:
1510:
1507:
1474:
1454:
1452:Fault tolerance
1404:
1310:
1271:tandem switches
1130:all-IP networks
1051:
1040:
1034:
1031:
1020:
1008:
989:
932:
880:
867:
866:
858:
856:
855:
854:
853:
850:
843:
840:
833:
827:
822:
698:
692:
684:crossbar switch
672:Strowger switch
596:
551:
475:
469:
368:
325:stepping switch
323:, patented the
267:tip-ring-sleeve
223:Charles Glidden
136:
74:telephone calls
28:
23:
22:
15:
12:
11:
5:
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2810:Space-division
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2700:
2699:
2689:
2683:
2681:
2673:
2672:
2670:
2669:
2664:
2659:
2654:
2649:
2647:Camille Tissot
2644:
2639:
2634:
2629:
2624:
2622:Claude Shannon
2619:
2614:
2612:Tivadar Puskás
2609:
2604:
2599:
2594:
2589:
2584:
2582:Antonio Meucci
2579:
2574:
2569:
2564:
2559:
2554:
2552:Charles K. Kao
2549:
2544:
2539:
2534:
2529:
2527:Harold Hopkins
2524:
2519:
2514:
2509:
2504:
2499:
2494:
2489:
2484:
2479:
2474:
2469:
2464:
2459:
2454:
2449:
2444:
2439:
2434:
2429:
2427:Emile Berliner
2424:
2419:
2414:
2409:
2404:
2399:
2394:
2388:
2386:
2382:
2381:
2379:
2378:
2373:
2368:
2366:Videotelephony
2363:
2358:
2357:
2356:
2351:
2341:
2334:
2329:
2323:
2318:
2313:
2308:
2303:
2302:
2301:
2296:
2291:
2281:
2280:
2279:
2269:
2264:
2262:Radiotelephone
2259:
2254:
2249:
2244:
2239:
2234:
2229:
2228:
2227:
2217:
2212:
2207:
2202:
2197:
2192:
2187:
2182:
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2172:
2167:
2166:
2165:
2160:
2155:
2150:
2148:Internet video
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2139:
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2128:
2123:
2113:
2108:
2103:
2098:
2093:
2088:
2082:
2080:
2074:
2073:
2066:
2065:
2058:
2051:
2043:
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2024:
2023:External links
2021:
2018:
2017:
1979:
1967:
1954:
1928:
1901:
1872:
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1820:
1801:
1779:
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1366:Integrated DLC
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1212:
1211:
1198:
1192:
1189:
1175:
1153:
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1141:
1133:
1124:
1123:
1105:Alcatel-Lucent
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1002:
988:
985:
965:British GPO/BT
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928:
879:
876:
857:
851:
841:
836:
835:
834:
825:
824:
823:
821:
818:
694:Main article:
691:
688:
623:telephone call
615:Almon Strowger
595:
592:
588:ringing signal
526:2L-4N or 2L-5N
503:common-battery
487:manual service
471:Main article:
468:
465:
447:common carrier
434:central office
430:
429:
420:
411:
402:
395:
388:
382:
375:Manual service
367:
364:
329:telephone dial
290:answering cord
275:telephone line
187:Tivadar Puskás
143:Tivadar Puskás
135:
132:
85:central office
66:central office
26:
9:
6:
4:
3:
2:
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3111:
3103:
3101:
3093:
3091:
3081:
3080:
3077:
3070:
3066:
3064:
3061:
3059:
3056:
3054:
3051:
3049:
3046:
3042:
3039:
3037:
3034:
3033:
3031:
3029:
3026:
3025:
3023:
3019:
3013:
3010:
3008:
3005:
3003:
3000:
2998:
2995:
2993:
2990:
2988:
2985:
2983:
2980:
2978:
2975:
2973:
2970:
2968:
2965:
2964:
2962:
2960:
2956:
2950:
2947:
2945:
2942:
2940:
2937:
2935:
2932:
2930:
2927:
2925:
2922:
2920:
2917:
2915:
2912:
2910:
2907:
2905:
2902:
2900:
2897:
2895:
2892:
2890:
2887:
2886:
2884:
2882:
2878:
2872:
2869:
2867:
2864:
2862:
2859:
2857:
2854:
2852:
2849:
2848:
2846:
2842:
2836:
2835:Code-division
2833:
2831:
2828:
2826:
2823:
2821:
2820:Time-division
2818:
2816:
2813:
2811:
2808:
2807:
2805:
2803:
2799:
2793:
2790:
2786:
2783:
2781:
2778:
2777:
2776:
2773:
2769:
2766:
2765:
2764:
2761:
2759:
2756:
2754:
2751:
2750:
2748:
2746:and switching
2744:
2740:
2732:
2729:
2728:
2727:
2724:
2720:
2717:
2716:
2715:
2712:
2710:
2707:
2705:
2702:
2698:
2697:optical fiber
2695:
2694:
2693:
2690:
2688:
2687:Coaxial cable
2685:
2684:
2682:
2680:
2674:
2668:
2665:
2663:
2660:
2658:
2655:
2653:
2650:
2648:
2645:
2643:
2640:
2638:
2635:
2633:
2630:
2628:
2625:
2623:
2620:
2618:
2615:
2613:
2610:
2608:
2605:
2603:
2602:Radia Perlman
2600:
2598:
2595:
2593:
2590:
2588:
2585:
2583:
2580:
2578:
2575:
2573:
2570:
2568:
2565:
2563:
2560:
2558:
2555:
2553:
2550:
2548:
2545:
2543:
2540:
2538:
2535:
2533:
2530:
2528:
2525:
2523:
2520:
2518:
2515:
2513:
2510:
2508:
2505:
2503:
2500:
2498:
2495:
2493:
2492:Lee de Forest
2490:
2488:
2487:Thomas Edison
2485:
2483:
2480:
2478:
2477:Donald Davies
2475:
2473:
2470:
2468:
2465:
2463:
2462:Claude Chappe
2460:
2458:
2455:
2453:
2450:
2448:
2445:
2443:
2440:
2438:
2435:
2433:
2430:
2428:
2425:
2423:
2420:
2418:
2415:
2413:
2410:
2408:
2405:
2403:
2400:
2398:
2395:
2393:
2390:
2389:
2387:
2383:
2377:
2374:
2372:
2369:
2367:
2364:
2362:
2359:
2355:
2352:
2350:
2347:
2346:
2345:
2342:
2340:
2339:
2335:
2333:
2330:
2327:
2324:
2322:
2319:
2317:
2314:
2312:
2309:
2307:
2306:Smoke signals
2304:
2300:
2297:
2295:
2292:
2290:
2287:
2286:
2285:
2284:Semiconductor
2282:
2278:
2275:
2274:
2273:
2270:
2268:
2265:
2263:
2260:
2258:
2255:
2253:
2250:
2248:
2245:
2243:
2240:
2238:
2235:
2233:
2230:
2226:
2223:
2222:
2221:
2218:
2216:
2213:
2211:
2208:
2206:
2203:
2201:
2198:
2196:
2193:
2191:
2188:
2186:
2183:
2181:
2178:
2176:
2173:
2171:
2168:
2164:
2161:
2159:
2156:
2154:
2151:
2149:
2146:
2145:
2144:
2143:Digital media
2141:
2137:
2134:
2132:
2129:
2127:
2124:
2122:
2119:
2118:
2117:
2114:
2112:
2109:
2107:
2104:
2102:
2099:
2097:
2094:
2092:
2089:
2087:
2084:
2083:
2081:
2079:
2075:
2071:
2064:
2059:
2057:
2052:
2050:
2045:
2044:
2041:
2035:
2032:
2030:
2027:
2026:
2007:on 2014-07-09
2003:
1999:
1998:
1990:
1983:
1974:
1972:
1964:
1961:Source: from
1958:
1944:on 2003-12-27
1943:
1939:
1932:
1918:
1911:
1905:
1891:on 2003-12-27
1890:
1886:
1879:
1877:
1867:
1853:on 2013-06-05
1849:
1842:
1836:
1829:
1824:
1816:
1812:
1805:
1797:
1793:
1789:
1783:
1774:
1760:on 2012-03-16
1759:
1755:
1749:
1734:
1730:
1724:
1709:
1705:
1699:
1691:
1687:
1681:
1673:
1671:9781587655227
1667:
1663:
1662:
1654:
1646:
1644:9780201767322
1640:
1636:
1635:
1630:
1624:
1617:
1616:
1611:
1610:
1605:
1600:
1592:
1588:
1582:
1578:
1568:
1565:
1563:
1560:
1558:
1555:
1553:
1550:
1548:
1545:
1543:
1540:
1538:
1535:
1533:
1530:
1528:
1525:
1524:
1520:
1509:
1502:
1500:
1495:
1494:optical fibre
1491:
1483:
1478:
1469:
1467:
1463:
1458:
1449:
1447:
1443:
1438:
1434:
1432:
1427:
1422:
1420:
1416:
1411:
1409:
1402:Switch design
1399:
1397:
1393:
1388:
1386:
1382:
1378:
1374:
1373:long distance
1369:
1367:
1362:
1359:
1358:Universal DLC
1354:
1352:
1348:
1344:
1341:Pair gain or
1339:
1337:
1333:
1329:
1324:
1322:
1317:
1315:
1314:outside plant
1301:
1293:
1289:
1287:
1283:
1279:
1274:
1272:
1266:
1263:
1259:
1255:
1251:
1246:
1244:
1240:
1236:
1235:sampling rate
1228:
1224:
1221:
1216:
1209:
1205:
1202:
1199:
1196:
1193:
1190:
1187:
1183:
1179:
1176:
1173:
1169:
1165:
1161:
1158:
1155:
1154:
1150:
1146:
1142:
1138:
1137:ITT System 12
1134:
1131:
1126:
1125:
1121:
1118:
1114:
1110:
1106:
1103:
1100:
1095:
1091:
1088:
1087:
1086:
1083:
1081:
1077:
1073:
1069:
1065:
1060:
1049:
1046:
1038:
1035:November 2023
1028:
1024:
1018:
1017:
1012:This section
1010:
1006:
1001:
1000:
993:
984:
982:
978:
972:
969:
966:
962:
958:
954:
951:
946:
944:
940:
936:
927:
925:
924:
919:
914:
912:
906:
903:
898:
892:
884:
875:
873:
865:
863:
839:
817:
814:
810:
805:
803:
800:
796:
792:
788:
783:
779:
777:
772:
770:
765:
763:
758:
756:
752:
748:
744:
740:
736:
734:
730:
726:
722:
719:Pulsing used
718:
713:
711:
707:
703:
697:
687:
685:
681:
680:Rotary system
677:
673:
669:
664:
661:
657:
653:
648:
646:
641:
639:
635:
631:
626:
624:
620:
616:
612:
608:
600:
591:
589:
585:
580:
578:
573:
568:
563:
561:
545:
541:
539:
534:
532:
527:
523:
518:
514:
512:
508:
504:
499:
496:
493:and asks the
492:
488:
479:
474:
464:
462:
458:
454:
451:
448:
444:
440:
435:
427:
426:
421:
418:
417:
412:
409:
408:
403:
400:
396:
393:
389:
386:
383:
380:
376:
373:
372:
371:
363:
360:
358:
354:
351:and later by
350:
345:
343:
339:
338:
332:
330:
326:
322:
318:
313:
310:
305:
301:
299:
295:
291:
287:
286:calling party
282:
280:
276:
272:
268:
264:
260:
255:
253:
250:
245:
243:
240:exchange (in
239:
235:
231:
226:
224:
220:
216:
212:
211:George W. Coy
208:
204:
200:
196:
192:
191:Thomas Edison
188:
185:
181:
176:
172:
169:
158:
150:
144:
140:
131:
129:
125:
120:
117:
113:
108:
106:
102:
98:
94:
90:
86:
82:
77:
75:
71:
67:
63:
59:
51:
46:
39:
34:
30:
19:
2802:Multiplexing
2791:
2677:Transmission
2642:Nikola Tesla
2632:Henry Sutton
2587:Samuel Morse
2517:Robert Hooke
2482:Amos Dolbear
2417:John Bardeen
2336:
2316:Telautograph
2220:Mobile phone
2175:Edholm's law
2158:social media
2091:Broadcasting
2009:. Retrieved
2002:the original
1995:
1982:
1957:
1946:. Retrieved
1942:the original
1931:
1920:. Retrieved
1916:
1904:
1893:. Retrieved
1889:the original
1866:
1855:. Retrieved
1848:the original
1835:
1823:
1814:
1804:
1796:the original
1792:cdrecord.org
1791:
1782:
1773:
1762:. Retrieved
1758:the original
1748:
1737:. Retrieved
1723:
1712:. Retrieved
1698:
1690:the original
1680:
1660:
1653:
1633:
1623:
1613:
1607:
1599:
1590:
1581:
1487:
1459:
1455:
1439:
1435:
1423:
1412:
1405:
1389:
1379:(PSTN), the
1370:
1365:
1363:
1357:
1355:
1340:
1325:
1318:
1311:
1281:
1277:
1275:
1267:
1247:
1232:
1084:
1056:
1041:
1032:
1021:Please help
1016:verification
1013:
973:
947:
933:
921:
917:
915:
907:
901:
896:
893:
889:
868:
859:
812:
806:
791:SF signaling
790:
786:
784:
780:
775:
773:
766:
759:
750:
746:
741:
737:
725:panel switch
714:
701:
699:
676:panel switch
665:
649:
645:supervision.
644:
642:
627:
611:dial service
610:
606:
605:
581:
564:
559:
557:
535:
522:panel switch
519:
515:
507:rotary dials
500:
486:
484:
460:
439:inside plant
433:
431:
423:
414:
407:concentrator
405:
398:
391:
385:Dial service
384:
374:
369:
361:
346:
335:
333:
314:
306:
302:
294:ringing cord
293:
289:
283:
279:cord circuit
256:
246:
227:
178:As with the
177:
173:
164:
121:
109:
105:rate centers
104:
96:
93:inside plant
84:
80:
78:
65:
61:
57:
55:
29:
3002:NPL network
2714:Radio waves
2652:Alfred Vail
2562:Hedy Lamarr
2547:Dawon Kahng
2507:Elisha Gray
2467:Yogen Dalal
2392:Nasir Ahmed
2326:Teleprinter
2190:Heliographs
1706:. Mszh.hu.
1248:Individual
953:1ESS switch
813:Robbed bits
733:rotary dial
729:dial pulses
710:Bell System
584:party lines
552: 1895
531:Bell System
457:local loops
399:wire center
366:Terminology
261:staffed by
259:plug boards
252:switchboard
97:wire center
89:Bell System
3135:Categories
3048:Antarctica
3007:Toasternet
2929:Television
2412:Paul Baran
2344:Television
2328:(teletype)
2321:Telegraphy
2299:transistor
2277:Phryctoria
2247:Photophone
2225:Smartphone
2215:Mass media
2011:2013-07-30
1948:2006-09-13
1922:2020-09-09
1895:2007-09-13
1857:2013-07-30
1764:2012-07-01
1739:2012-07-01
1714:2012-07-01
1573:References
1547:Softswitch
1398:receiver.
1334:(ISDN) or
1250:local loop
1115:, and the
943:reed relay
862:media help
721:quaternary
337:linefinder
271:subscriber
234:Manchester
219:Bridgeport
3151:Telephony
3032:Americas
3021:Locations
2992:Internet2
2753:Bandwidth
2457:Vint Cerf
2354:streaming
2332:Telephone
2272:Semaphore
2163:streaming
1615:The Times
1431:be called
1419:time slot
1328:pair gain
1282:satellite
1097:Ericsson
1059:Bell Labs
897:make-busy
809:T-carrier
704:. Before
634:dial tone
630:telephone
560:MAin 1234
538:indicator
513:or idle.
342:dial tone
249:multiplex
184:Hungarian
101:dial tone
50:broadband
3100:Category
2987:Internet
2977:CYCLADES
2894:Ethernet
2844:Concepts
2768:terminal
2719:wireless
2542:Bob Kahn
2385:Pioneers
2210:Internet
2101:Cable TV
1733:Archived
1708:Archived
1631:(2002).
1505:See also
1208:BT Group
1204:System X
1113:1000-S12
1090:Ericsson
1080:Brittany
1072:Strowger
902:TD tool.
747:keypulse
682:and the
572:Dry cell
495:operator
491:off-hook
416:off-hook
353:crossbar
309:ringdown
3120:Commons
3110:Outline
3063:Oceania
2982:FidoNet
2967:ARPANET
2780:circuit
2349:digital
2078:History
1704:"SZTNH"
1629:Bo Leuf
1444:, or a
1338:(DSL).
1260:as the
1223:DMS-100
1201:Marconi
1182:Genband
1164:Siemens
1109:Alcatel
1076:Alcatel
795:falsing
567:magneto
511:on-hook
425:on-hook
307:In the
284:When a
242:Antwerp
134:History
3058:Europe
3028:Africa
3012:Usenet
2972:BITNET
2909:Mobile
2785:packet
2294:MOSFET
2289:device
2086:Beacon
1668:
1641:
1415:space-
1351:Lucent
1278:remote
1227:France
1220:Nortel
1186:DMS100
1178:Nortel
1172:DeTeWe
1140:world.
1064:London
702:trunks
668:relays
658:, and
230:London
203:Berlin
199:Boston
168:schema
3041:South
3036:North
2997:JANET
2934:Telex
2924:Radio
2763:Nodes
2758:Links
2679:media
2257:Radio
2242:Pager
2170:Drums
2136:video
2131:image
2121:audio
2005:(PDF)
1992:(PDF)
1913:(PDF)
1851:(PDF)
1844:(PDF)
1180:then
1168:Bosch
1111:E10,
872:cards
820:Noise
755:CCITT
751:start
660:9-1-1
485:With
298:trunk
3053:Asia
2939:UUCP
2899:ISDN
1666:ISBN
1639:ISBN
1424:The
1258:ETSI
1170:and
1160:EWSD
1149:4ESS
1147:and
1145:5ESS
1120:5ESS
638:DTMF
357:DTMF
254:. .
232:and
161:(F).
83:and
2944:WAN
2914:NGN
2904:LAN
2185:Fax
2126:DCT
1280:or
1239:PCM
1195:NEC
1092:'s
1025:by
981:SS7
968:TXE
961:PRX
957:SP1
807:On
789:or
422:An
413:An
273:'s
197:in
64:or
3137::
1994:.
1970:^
1915:.
1875:^
1813:.
1790:.
1606:,
1589:.
1501:.
1448:.
1273:.
1262:V5
1166:,
804:.
708:,
686:.
678:,
579:.
549:c.
432:A
404:A
397:A
390:A
281:.
209:.
56:A
36:A
3071:)
3067:(
2062:e
2055:t
2048:v
2014:.
1965:.
1951:.
1925:.
1898:.
1860:.
1830:.
1817:.
1767:.
1742:.
1717:.
1674:.
1647:.
1484:.
1132:.
1122:.
1048:)
1042:(
1037:)
1033:(
1019:.
864:.
554:)
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
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