427:. This also uses audio tones, but these are not restricted to sub-audio tones and are sent as a short burst in sequence. The receiver will be programmed to respond only to a unique set of tones in a precise sequence, and only then will it open the audio circuits for open-channel conversation with the base station. This system is much more versatile than CTCSS, as relatively few tones yield a far greater number of "addresses". In addition, special features (such as broadcast modes and emergency overrides) can be designed in, using special addresses set aside for the purpose. A mobile unit can also broadcast a Selcall sequence with its unique address to the base, so the user can know before the call is picked up which unit is calling. In practice many selcall systems also have automatic
420:, or Continuous Tone-Controlled Squelch System. This consists of superimposing a precise very low frequency tone on the audio signal. Only the receiver tuned to this specific tone turns the signal into audio: this receiver shuts off the audio when the tone is not present or is a different frequency. By assigning a unique frequency to each mobile, private channels can be imposed on a public network. However this is only a convenience feature—it does not guarantee privacy.
662:(FCC) has issued various commercial "radiotelephone operator" licenses and permits to qualified applicants. These allow them to install, service, and maintain voice-only radio transmitter systems for use on ships and aircraft. (Until deregulation in the 1990s they were also required for commercial domestic radio and television broadcast systems. Because of treaty obligations they are still required for engineers of international
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301:, operation, which allows one person to talk and the other to listen alternately. If a single frequency is used, both parties take turns to transmit on it, known as simplex. Dual-frequency working or duplex splits the communication into two separate frequencies, but only one is used to transmit at a time with the other frequency dedicated to receiving.
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Often, on a small network system, there are many mobile units and one main base station. This would be typical for police or taxi services for example. To help direct messages to the correct recipients and avoid irrelevant traffic on the network being a distraction to other units, a variety of means
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Marine radiotelephony first became common in the 1930s, and was used extensively for communications to ships and aircraft over water. In that time, most long-range aircraft had long-wire antennas that would be let out during a call, and reeled-in afterward. Marine radiotelephony originally used AM
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built in, which allows the base station to "interrogate" a mobile even if the operator is not present. Such transponding systems usually have a status code that the user can set to indicate what they are doing. Features like this, while very simple, are one reason why they are very popular with
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allowed a mobile unit to have a telephone number allowing access from the general telephone network, although some systems required mobile operators to set up calls to mobile stations. Mobile radio telephone systems before the introduction of
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Single-sideband (SSB) is used because the short wave bands are crowded with many users, and SSB permits a single voice channel to use a narrower range of radio frequencies (bandwidth) when compared to earlier AM systems. SSB uses about 3.5
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The user presses a special switch on the transmitter when they wish to talk—this is called the "press-to-talk" switch or PTT. It is usually fitted on the side of the microphone or other obvious position. Users may use a
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and presents some technical challenges. It is, however, the most comfortable method of voice communication for users, and it is currently used in cell phones and was used in the former
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organisations that need to manage a large number of remote mobile units. Selcall is widely used, though is becoming superseded by much more sophisticated digital systems.
258:. This would include systems fitting into the category of two-way radio or one-way voice broadcasts such as coastal maritime weather. The term is still popular in the
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mode in the 2-3 MHz region before the transition to SSB and the adoption of various higher frequency bands in addition to the 2 MHz frequencies.
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design. Likewise, transmitters are carefully designed to avoid unwanted interference and feature power outputs from a few tens of milliwatts to perhaps 50
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740:"Signal training (all arms). Pamphlet no. 5 : signal procedure. Part III : combined joint radiotelephone (RT) procedure 1943"
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One of the most important uses of marine radiotelephony has been to change ships' itineraries, and to perform other business at sea.
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Most shore stations monitor several frequencies. The frequencies with the longest range are usually near 20
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where they are licensed to do so, though typically they are used in the various bands between 60 and 900
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and the ground, giving a modest 1,000 watt transmitter (the standard power) a worldwide range.
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services suffered from few usable channels, heavy congestion, and very high operating costs.
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has a long precedent beginning with early US wired voice systems. The term means
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779:"Guide to Radio Communications Standards for DEM Emergency Responders"
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788:. Rhode Island Department of Environmental Management. Archived from
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are usually designed to a very high standard, and are usually of the
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840:"Radiotelephone | Museum of Maritime Navigation and Communication"
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band from 118.0 to 136.975 MHz, using amplitude modulation.
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such as "over" to signal that they have finished transmitting.
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broadcast stations.) The certificate currently issued is the
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and 960 MHz in the United States). They may use simple
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A more commonly used system is called selective calling or
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Communications system for transmission of speech over radio
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for a mobile unit, up to a couple of hundred watts for a
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The most common method of working for radiotelephones is
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Short wave radio is used because it bounces between the
861:"Radiotelephone System for Harbor and Coastal Services"
341:, or more complex techniques such as digital coding,
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505:. Unsourced material may be challenged and removed.
67:. Unsourced material may be challenged and removed.
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936:Bell: Alexander Bell and the Conquest of Solitude
958:Alexander Graham Bell: Giving Voice To The World
413:have been devised to create addressing systems.
372:. Multiple channels are often provided using a
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8:
765:"47 CFR 95.141 - Interconnection prohibited"
2024:Global telecommunications regulation bodies
859:Anderson, C.N.; Pruden, H.M. (April 1939).
398:receivers, which often dispense with this.
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416:The crudest and oldest of these is called
390:output from the receiver when there is no
565:Learn how and when to remove this message
127:Learn how and when to remove this message
229:, and in some radio services, including
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668:general radiotelephone operator license
394:to listen to. This is in contrast to
7:
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503:adding citations to reliable sources
65:adding citations to reliable sources
317:Radiotelephones may operate at any
209:and sound. The term is related to
815:"The Evolution of Shortwave Radio"
25:
700:Improved Mobile Telephone Service
680:Air-ground radiotelephone service
660:Federal Communications Commission
639:(voice or communication-quality)
595:public switched telephone network
460:Improved Mobile Telephone Service
264:Federal Communications Commission
233:, interconnection is prohibited.
195:, which is radio transmission of
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1659:Free-space optical communication
685:ASTRA2Connect Maritime Broadband
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41:
490:needs additional citations for
189:by radio. It is in contrast to
52:needs additional citations for
2111:Wireless communication systems
954:Carson, Mary Kay (2007). "8".
1:
579:Marine Radiotelephone Service
402:Privacy and selective calling
2045:Telecommunication portal
1826:Telecommunications equipment
379:Receivers usually feature a
32:Photophone § Radiophone
1562:Alexander Stepanovich Popov
635:uses about 8 kHz, and
254:as opposed to telegraph or
2127:
1266:Telecommunications history
877:10.1109/JRPROC.1939.228232
690:AT&T High Seas Service
591:single-sideband modulation
444:
441:Conventional telephone use
405:
362:double-conversion superhet
29:
2101:Mobile telecommunications
2033:
1874:Public Switched Telephone
1686:telecommunication circuit
1647:Fiber-optic communication
1392:Francis Blake (telephone)
1187:Optical telecommunication
589:radio frequencies, using
1785:Orbital angular-momentum
1222:Satellite communications
1061:Communications satellite
940:Cornell University Press
715:Mobile Telephone Service
605:telephone and email via
456:Mobile Telephone Service
177:system for conducting a
30:Not to be confused with
1664:Molecular communication
1487:Gardiner Greene Hubbard
1316:Undersea telegraph line
1051:Cable protection system
2096:Maritime communication
1806:Communication protocol
1592:Charles Sumner Tainter
1407:Walter Houser Brattain
1352:Edwin Howard Armstrong
1160:Information revolution
907:"List of FCC Licenses"
865:Proceedings of the IRE
710:Mobile radio telephone
452:Mobile radio telephone
447:Mobile radio telephone
280:communication channels
158:
1780:Polarization-division
1512:Narinder Singh Kapany
1477:Erna Schneider Hoover
1397:Jagadish Chandra Bose
1377:Alexander Graham Bell
1108:online video platform
374:frequency synthesizer
142:
1622:Vladimir K. Zworykin
1582:Almon Brown Strowger
1552:Charles Grafton Page
1207:Prepaid mobile phone
1135:Electrical telegraph
938:. Ithaca, New York:
744:Imperial War Museums
499:improve this article
307:procedural code-word
262:community and in US
148:handheld transceiver
61:improve this article
2106:Telephony equipment
1572:Johann Philipp Reis
1331:Wireless revolution
1293:The Telephone Cases
1150:Hydraulic telegraph
175:radio communication
1770:Frequency-division
1747:Telephone exchange
1617:Charles Wheatstone
1547:Jun-ichi Nishizawa
1522:Innocenzo Manzetti
1457:Reginald Fessenden
1192:Optical telegraphy
1025:Telecommunications
607:satellite internet
465:cellular telephone
270:Modes of operation
211:radio broadcasting
205:, transmission of
159:
2083:
2082:
1821:Store and forward
1816:Data transmission
1730:Network switching
1681:Transmission line
1527:Guglielmo Marconi
1492:Internet pioneers
1357:Mohamed M. Atalla
1326:Whistled language
973:978-1-4027-3230-0
934:Bruce, Robert V.
643:uses 9 kHz.
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408:Selective calling
227:telephone network
143:Comparison of an
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16:(Redirected from
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1914:Notable networks
1904:Wireless network
1844:Cellular network
1836:Types of network
1811:Computer network
1698:Network topology
1612:Thomas A. Watson
1467:Oliver Heaviside
1452:Philo Farnsworth
1427:Daniel Davis Jr.
1402:Charles Bourseul
1362:John Logie Baird
1071:Data compression
1066:Computer network
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909:. Archived from
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795:on 14 April 2018
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1557:Radia Perlman
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1447:Lee de Forest
1445:
1443:
1442:Thomas Edison
1440:
1438:
1435:
1433:
1432:Donald Davies
1430:
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1417:Claude Chappe
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1261:Smoke signals
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1239:Semiconductor
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1098:Digital media
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948:0-8014-9691-8
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913:on 2009-02-15
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721:
720:Two-way radio
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537:
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530:
526:
523:
519:
516: –
515:
511:
510:Find sources:
504:
500:
494:
493:
488:This article
486:
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269:
267:
266:regulations.
265:
261:
260:amateur radio
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215:two-way radio
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145:amateur radio
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88:
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81:
78: –
77:
73:
72:Find sources:
66:
62:
56:
55:
50:This article
48:
44:
39:
38:
33:
19:
1757:Multiplexing
1632:Transmission
1597:Nikola Tesla
1587:Henry Sutton
1542:Samuel Morse
1472:Robert Hooke
1437:Amos Dolbear
1372:John Bardeen
1291:
1271:Telautograph
1216:
1175:Mobile phone
1130:Edholm's law
1113:social media
1046:Broadcasting
957:
935:
915:. Retrieved
911:the original
901:
868:
864:
854:
843:. Retrieved
834:
823:. Retrieved
821:. 2016-08-01
818:
809:
797:. Retrieved
790:the original
785:
773:
759:
747:. Retrieved
743:
734:
657:
649:
645:
625:
618:
611:
585:operates on
582:
578:
576:
561:
552:
542:
535:
528:
521:
509:
497:Please help
492:verification
489:
450:
429:transponding
422:
415:
411:
392:transmission
378:
370:base station
355:
316:
303:
296:
273:
251:
247:
245:
223:marine radio
200:
190:
182:
179:conversation
170:
166:
162:
160:
123:
114:
104:
97:
90:
83:
71:
59:Please help
54:verification
51:
1957:NPL network
1669:Radio waves
1607:Alfred Vail
1517:Hedy Lamarr
1502:Dawon Kahng
1462:Elisha Gray
1422:Yogen Dalal
1347:Nasir Ahmed
1281:Teleprinter
1145:Heliographs
819:Radio World
654:Regulations
299:half-duplex
284:full-duplex
274:A standard
2090:Categories
2003:Antarctica
1962:Toasternet
1884:Television
1367:Paul Baran
1299:Television
1283:(teletype)
1276:Telegraphy
1254:transistor
1232:Phryctoria
1202:Photophone
1180:Smartphone
1170:Mass media
929:References
917:2009-01-27
845:2022-04-25
825:2022-04-25
799:8 February
637:narrowband
614:ionosphere
555:April 2022
525:newspapers
471:Marine use
331:modulation
256:Morse code
202:television
167:radiophone
152:cell phone
117:April 2012
87:newspapers
1987:Americas
1976:Locations
1947:Internet2
1708:Bandwidth
1412:Vint Cerf
1309:streaming
1287:Telephone
1227:Semaphore
1118:streaming
982:182527281
885:0096-8390
695:Car phone
664:shortwave
587:shortwave
396:broadcast
358:receivers
319:frequency
288:bandwidth
246:The word
197:telegrams
187:telephony
2055:Category
1942:Internet
1932:CYCLADES
1849:Ethernet
1799:Concepts
1723:terminal
1674:wireless
1497:Bob Kahn
1340:Pioneers
1165:Internet
1056:Cable TV
942:, 1990.
893:51653876
749:20 April
705:Inmarsat
674:See also
633:AM radio
631:, while
599:INMARSAT
313:Features
276:landline
219:CB radio
156:matchbox
2075:Commons
2065:Outline
2018:Oceania
1937:FidoNet
1922:ARPANET
1735:circuit
1304:digital
1033:History
539:scholar
425:Selcall
384:circuit
381:squelch
347:airband
173:, is a
101:scholar
2013:Europe
1983:Africa
1967:Usenet
1927:BITNET
1864:Mobile
1740:packet
1249:MOSFET
1244:device
1041:Beacon
980:
970:
946:
891:
883:
601:) and
541:
534:
527:
520:
512:
237:Design
185:means
154:, and
103:
96:
89:
82:
74:
1996:South
1991:North
1952:JANET
1889:Telex
1879:Radio
1718:Nodes
1713:Links
1634:media
1212:Radio
1197:Pager
1125:Drums
1091:video
1086:image
1076:audio
966:–78.
889:S2CID
793:(PDF)
782:(PDF)
726:Notes
546:JSTOR
532:books
418:CTCSS
388:audio
366:watts
252:voice
248:phone
108:JSTOR
94:books
2008:Asia
1894:UUCP
1854:ISDN
978:OCLC
968:ISBN
944:ISBN
881:ISSN
801:2018
751:2021
603:VoIP
577:The
518:news
458:and
436:Uses
292:IMTS
231:GMRS
165:(or
80:news
1899:WAN
1869:NGN
1859:LAN
1140:Fax
1081:DCT
873:doi
786:DEM
629:kHz
621:MHz
581:or
501:by
351:VHF
337:or
323:MHz
221:or
63:by
2092::
976:.
964:76
887:.
879:.
869:27
867:.
863:.
817:.
784:.
742:.
670:.
641:FM
609:.
376:.
339:FM
335:AM
327:25
294:.
181:;
171:RT
161:A
150:,
2026:)
2022:(
1017:e
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920:.
895:.
875::
848:.
828:.
803:.
767:.
753:.
568:)
562:(
557:)
553:(
543:·
536:·
529:·
522:·
495:.
325:(
130:)
124:(
119:)
115:(
105:·
98:·
91:·
84:·
57:.
34:.
20:)
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