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on opposite sides of the
Toronto-Mississauga boundary are examples where each exchange serves clients on both sides of a county line using different rate centres. A client in Mississauga requesting a Toronto number would be charged FX line rates, despite the Toronto numbers being on the same physical
109:
of the foreign exchange. The telecommunication circuit between central offices that implements foreign exchange service has complementary interface types at each end. At the foreign central office that provides the service, the interface is called the foreign exchange office (FXO) end, and at the end
153:
The prefixes often still reflected the geography and had value in user's perception of the number, beyond the pure technical function of uniquely identifying the central office. Calls with a different prefix might incur additional charges, so businesses on one central office might want a number that
241:
Originally, the FX line was a physical copper pair of telephone wires from the foreign exchange which were connected to the local subscriber loop at the local exchange, without passing through the local switch. This dedicated circuit is often replaced with a virtual circuit, where the local switch
264:
An outbound "extender" is an automated local number at a service bureau in the larger city. A suburban subscriber (who can call the city itself locally but is long distance to suburbs on the other side) could call the extender locally, get a city dial tone and dial back out locally to the larger
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The circuit that implements the foreign exchange service has two ends, one at the central office that provides the service in the foreign exchange, where the telephone number is assigned, and one at the central office that services the subscriber station. The former is called a foreign exchange
187:
A subscriber located just outside the exchange boundary of a large city, or just outside the flat-rate local calling area for the city, would find that many numbers which would have been local from the city itself became long-distance. In many areas, local flat-rate service was subsidized by
176:(FX). They differ only in that the remote office is in exactly the same rate centre (FCO) or merely in a different zone of the same US metropolitan city (FZ). Much like FX service rates depend on the distance between rate centers, FCO service prices depend on the distance between exchanges.
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Customers who wanted a telephone number provided by a neighboring or remote telephone central office leased a "foreign exchange" line. With two-wire loop technology, this typically required an engineered circuit with increased costs. The practice, rare except in big cities, is in decline.
237:
While a cost of hundreds of dollars monthly for the leased line was not uncommon, to a business handling large volumes of calls from the larger city the cost may have been justified by long-distance toll savings at a time when long-distance was pricey and alternatives were limited.
129:
Basic telephony terminology distinguishes two types of offices: local and foreign. A local office is assigned a specific area, and all telephone services provided to that area originate from that central office. Each central office has a unique identifier. The
271:
served a similar function for inbound calls only. A suburban business could get a downtown big-city number; clients anywhere in the larger city's coverage area could call locally, only to be silently redirected via a second local call to the
278:
systems have been hosted at answering service bureaux for clients such as suburban radio stations accepting calls from listeners in the larger city. As the machine is on a city number, it is reachable from the full metropolitan calling
371:
Some of the terminology of the foreign exchange service is retained in modern digital packet telephony to indicate whether VoIP equipment is designed to be connected to telephone lines from a central office or to telephone stations.
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A similar "FCO" service provided no difference in local calling area (the distant exchange is in the same rate centre). Historically, it was a means to obtain features not available on the local exchange (such as
632:
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is local call for customers of a different central office. Prefixes, since they related to geography, often carried the cachet of their neighborhoods; some central office prefixes were
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long-distance toll service for much of the 20th century. As an "FX line" has a number from the neighboring city, it has the city calling area for both incoming and outbound calls.
146:, derived from locally-distinct geographic or historical contexts. Under the standardized number plan, each central office was assigned a three-digit number unique within each
17:
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If the business is located just outside the larger city's local calling area, an FX number in the next-closer suburb would provide a limited coverage of the city. An
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numbers may be obtained from most cities and used almost anywhere in the world. VoIP renders the subscriber's physical location meaningless, as long as unrestricted
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An FXS interface is any interface that functions like a standard telephone line jack on the wall. An FXS interface utilizes a line protocol, most commonly
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that terminates the foreign exchange line at the central office that provides the telephone number and the call switching for the service. It generates the
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office (FXO) interface, and the latter a foreign exchange station (FXS) interface. These two interface types perform complementary functions in signaling.
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303:) which can then be freely moved out of the original geographic location while keeping the directory listing and service area unchanged.
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exchanges (in countries which use geographic numbers) normally are issued from the larger city and have that city's full calling area.
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The foreign exchange station (FXS) interface is located at the wire center of the subscriber equipment, supplying battery power and
451:
Jones, Graham A.; Layer, David H.; Osenkowsky, Thomas G. (2007). Williams, Edmund A.; National
Association of Broadcasters (eds.).
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indications through loop closure and non-closure of a direct current (DC) circuit powered by the serving central office switch.
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tone dialling when first introduced in 1963) or keep an existing business telephone number operational after a cross-town move.
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at the same location, but clients were billed based on nominal centre-to-centre distance between different rate centres.
135:
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as that community is local to both
Toronto and Oshawa, even though Ajax does not have the full Toronto calling area.
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Conventional "foreign exchange" leased lines and their variants have become less common due to newer alternatives:
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The FXO and FXS terminology is frequently used outside of the context of foreign exchange links. Examples include
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FXO and FXS interfaces are available for computers and networking equipment to interface these directly with
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207:) a local number will reach the city but not the suburbs on the other side. Adding an FX line with a Toronto
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where the subscriber station is connected, it provides the foreign exchange station (FXS) interface.
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exchange, rather than the local exchange area where the subscriber station equipment is located. To
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sends the FX calls to the foreign exchange (which handles all billing) on existing trunks.
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In rare instances, the supposed "foreign" exchange actually resided on the same physical
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The "FX line" is usually treated as part of the distant city when originating calls to
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An FX line has the local calling area of the foreign exchange in which it is numbered.
172:(FZ) services were, from a technological standpoint, deployed with the same methods as
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having the FX service is located in the foreign exchange area. It is assigned a
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A foreign exchange office (FXO) device plays the role of an analog phone.
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allows an existing number to be moved to VoIP (or, in some countries, a
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For instance, a suburban business may want to market extensively to
50:) refer to the different ends of a telephone line in the context of
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http://www.localcallingguide.com/lca_prefix.php?switch=MALTON22CG1
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http://www.localcallingguide.com/lca_prefix.php?switch=TOROON29DS0
386:, appears to be a telephone. As such, it should be able to accept
58:. The FXO side is used for the telephone, and the FXS side is the
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toward the subscriber station of the foreign exchange service.
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An FXO device is any device that, from the point of view of a
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453:
National
Association of Broadcasters Engineering handbook
409:, to detect when the terminating device (telephone) goes
528:. AT&T Wholesale – Southeast Region. Archived from
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or central office in another exchange area, called the
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199:If the business is in an adjacent suburb (such as
150:that was prefixed to the local telephone number.
329:The foreign exchange office (FXO) interface is a
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390:, go on-hook and off-hook, and send and receive
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195:, a large city with flat-rate local calling:
85:in a given exchange area is connected, via a
18:Foreign exchange service (telecommunications)
218:business may lease an FX line from suburban
54:(VoIP) systems and its interconnection with
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417:, and can send and receive voice signals.
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27:For the use of this term in finance, see
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230:-style numbers, such as information or
14:
670:
510:: CS1 maint: archived copy as title (
89:, as opposed to a switched line, to a
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211:number would provide full coverage.
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572:"Virtual foreign exchange service"
526:"Products & Services – Resale"
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101:originators, it appears that the
631: This article incorporates
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663:Differences between FXS and FXO
644:General Services Administration
156:immortalized in popular culture
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432:Telephone signaling interfaces
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1:
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331:telephone signaling interface
134:established a unified set of
361:Use in voice-over-IP systems
7:
603:"Atlanta Telephone History"
574:– via Google Patents.
420:
377:plain old telephone service
232:emergency telephone numbers
179:
77:was an access service in a
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704:
364:
295:is available at the site.
276:Interactive voice response
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79:telecommunications network
56:analog telephony equipment
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367:Analog telephone adapter
345:Foreign exchange station
297:Local number portability
138:after World War II. The
136:central offices prefixes
60:analog telephone adapter
44:foreign exchange station
325:Foreign exchange office
36:foreign exchange office
29:Foreign exchange market
683:Communication circuits
639:Federal Standard 1037C
633:public domain material
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269:Remote call forwarding
166:Foreign central office
34:In modern day usage, "
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394:signals. It may use
678:Telephone exchanges
384:telephone exchange
316:Circuit interfaces
313:
293:broadband Internet
247:telephone exchange
91:telephone exchange
688:Telephony signals
466:978-0-240-80751-5
455:(10th ed.).
353:, and generating
158:for that reason.
16:(Redirected from
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379:(POTS) systems.
301:mobile telephone
283:Mobile telephone
174:foreign exchange
107:telephone number
67:foreign exchange
65:Historically, a
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459:. p. 614.
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392:voice frequency
388:ringing signals
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355:ringing voltage
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140:central offices
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657:External links
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650:on 2022-01-22.
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609:on 2016-05-10
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648:the original
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558:cpr.att.com
551:"Ilec-Ohio"
457:Focal Press
402:signaling.
201:Mississauga
132:Bell System
81:in which a
672:Categories
613:2014-10-10
536:2014-10-10
497:2014-10-10
438:References
407:loop start
396:loop start
365:See also:
351:dial tone
168:(FCO) or
148:area code
83:telephone
506:cite web
421:See also
415:off-hook
335:off-hook
180:Function
592:switch.
411:on-hook
339:on-hook
205:Markham
193:Toronto
125:Purpose
121:links.
95:foreign
75:service
42:) and "
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216:Oshawa
209:+1-416
635:from
554:(PDF)
491:(PDF)
484:(PDF)
279:area.
265:area.
144:names
117:with
587:and
512:link
461:ISBN
337:and
255:DTMF
220:Ajax
99:call
413:or
398:or
228:N11
203:or
48:FXS
46:" (
40:FXO
38:" (
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508:}}
504:{{
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119:T1
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71:FX
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69:(
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