129:
486:
141:
262:
198:
432:
2590:
250:
210:
373:
32:
2600:
389:
2579:
2610:
174:" button, which turns off the receiver and turns on the transmitter; when the button is released, the receiver is activated again. Multiple channels are provided so separate user groups can communicate in the same area without interfering with each other and some radios are designed to scan the channels in order to find a valid transmission. Other two-way radio systems operate in
170:, in which transmission can only be sent in one direction, and full-duplex, which allows transmission in both directions simultaneously.) This requires users in a group to take turns talking. The radio is normally in receive mode so the user can hear all other transmissions on the channel. When the user wants to talk, they press a "
364:, and estimate how well signals will penetrate buildings. These models will be backed-up by drive testing and actual field signal level measurements. Designers adjust antenna patterns, add or move equipment sites, and design antenna networks in a way that will accomplish the intended level of performance.
493:
Typical two-way radios work on fixed radio frequency channels, though some can scan multiple channels in order to find a valid transmission. In an analog, conventional system, (the simplest type of system) a frequency or channel serves as a physical medium or link carrying communicated information.
325:
Analog systems may communicate a single condition, such as water level in a livestock tank. A transmitter at the tank site continually sends a signal with a constant audio tone. The tone would change in pitch to indicate the tank's water level. A meter at the remote end would vary, corresponding to
409:
In government systems, equipment may be replaced based on budgeting rather than any plan or expected service life. Funding in government agencies may be cyclical or sporadic. Managers may replace computing systems, vehicles, or budget computer and vehicle support costs while ignoring two-way radio
343:
button, sending data in the opposite direction and flagging the call as received by the driver. They can be used for analog telemetry systems, such as the livestock tank levels, as described above. Another possibility is the lubricating oil pressure in a transit bus engine, or the current speed of
417:
Another source says system backbone equipment like consoles and base stations are expected to have a fifteen-year life. Mobile radios are expected to last ten years. Walkie talkies typically last eight. In a State of
California document, the Department of General Services reports expected service
384:
Many mobile and handhelds have a limited duty cycle. Duty Cycle is the ratio of listening time to transmit time and is generally dependent on how well the transmitter can shed the heat from the heat sink on the rear of the radio. A 10% duty cycle (common on handhelds) translates to 10 seconds of
359:
or standard. They are designed as systems with all equipment matched to perform together. For example, a modern, local government two-way radio system in the US may be designed to provide 95% area coverage in an urban area. System designers use radio frequency models, terrain models, and signal
413:
One document says "seven years" is beyond the expected lifetime of walkie-talkies in police service. Batteries are cited as needing replacement more often. Twelve-year-old dispatch consoles mentioned in the same document were identified as usable. These were compared to problematic 21-year-old
315:
Disadvantage: If a radio cannot reach the repeater, it cannot communicate. This can be mitigated with a "talk around" or "car to car" setting where stations out of range of the base can speak directly to each other, alternating transmitting and receiving roles in simplex fashion on a single
832:, Soviet Military Thought Series #18, (Washington, D.C.: Superintendent of Documents, 1977) Library of Congress Control Number: 84602565. This is a US Air Force translation of a Soviet-era, Russian-language book. See also, "Inadequate System Capacity,"
229:
were the first in the world to use wireless communication in cars, putting an end to the inefficient status reports via public telephone boxes which had been used until that time. The first sets occupied about half of the floor in the back seat of the
330:. In the US, mid-band 72–76 MHz or UHF 450–470 MHz interstitial channels are often used for these systems. Some systems multiplex telemetry of several analog conditions by limiting each to a separate range of tone pitches, for example.
298:
set standards for channel access times and delays caused by system overhead. Scan features can further increase these delays. One study said delays of longer than 0.4 seconds (400 milliseconds) in emergency services are not recommended.
128:
338:
Digital systems may communicate text messages from computer-aided dispatch (CAD). For example, a display in a tow truck may give a textual location for a call and any related details. The tow truck driver may press an
311:
Advantage: duplex channels usually allow repeater operation which extends range (in most cases due to increased transmit power and improved aerial location / height) – especially where hand-held radios are in
967:, November 1964, pp. 2935-2971. 800 MHz trivia: this article shows that signal fades occur at audio frequencies near CTCSS tones, explaining why only DCS was used in Motorola 800 MHz systems in the 1970s.
919:
Planning
Emergency Medical Communications: Volume 2, Local/Regional-Level Planning Guide, (Washington, D.C.: National Highway Traffic Safety Administration, US Department of Transportation, 1995) pp. 48.
326:
the tone pitch, to indicate the amount of water present in the livestock tank. Similar methods can be used to telemeter any analog condition. This type of radio system serves a purpose equivalent to a
241:
police department successfully operated a two-way system between a central fixed station and radio transceivers installed in police cars; this allowed rapidly directing police response in emergencies.
344:
the bus. Analog conditions are translated into data words. Some systems send radio paging messages which can either 1) beep a paging receiver, 2) send a numeric message, or 3) send a text message.
166:
Two-way radios usually use a half-duplex communication channel, which permits two-way communication, albeit with the limitation that only one user can transmit at a time. (This is in contrast to
550:
has become an important activity of governments to regulate radio users in the interests of both efficient and non-interfering use of radio. Both bands are widely applied for different users.
360:
propagation modeling software in an attempt to accurately estimate where radios will work within a defined geographic area. The models help designers choose equipment, equipment locations,
163:), which is used for bidirectional person-to-person voice communication with other users with similar radios, in contrast to a broadcast receiver, which only receives transmissions.
494:
The performance of a radio system is partly dependent on the characteristics of frequency band used. The selection of a frequency for a two-way radio system is affected, in part, by:
1122:
385:
transmit time to 90 seconds of receive time. Some mobile and base equipment is specified at different power levels – for example 100% duty cycle at 25 watts and 15% at 40 watts.
307:
The term "half duplex" is applied to wired communication systems where the circuit can send information in one direction at a time but not both directions at the same time.
895:
USFA-TR-099/January 1999, (Emmitsburg, Maryland: U.S. Fire
Administration, 1999) pp. 25-26. This article also confirms the definition of the phrase talk around.
1854:
824:
One example of purpose-specific channel assignments is described in Ivanov, D. A., V. P. Savelyev, and P. V. Shemanski, "Organization of
Communications,"
813:
960:
Ossanna, Jr., Joseph F., "A Model For Mobile Radio Fading Due to
Building Reflections: Theoretical and Experimental Fading Waveform Power Spectra,"
185:
The first two-way radio was an AM-only device introduced by the Galvin
Manufacturing Corporation in 1940 for use by the police and military during
442:
987:
For one example, see: "Plan
Element S-7: Rationalized Funding" and "Plan Element L-2: Permanent Contra Costa Public Safety Radio Authority,"
2562:
2534:
2529:
1554:
930:
178:
mode, in which both parties can talk simultaneously. This requires either two separate radio channels or channel sharing methods such as
1158:
410:
equipment. Equipment may remain in use even though maintenance costs are unreasonable when viewed from an efficiency standpoint.
957:, 80-C477, (Sacramento, California: Department of General Services, Communications Technology Division, 1982,) pp. II-1 - II-34.
2556:
1008:, (Oklahoma City, Oklahoma: Oklahoma City Municipal Facilities Authority, Public Safety Capital Projects Office, 2000) pp. 56.
2551:
2541:
2521:
2323:
878:"IEEE 100 The Authoritative Dictionary of IEEE Standards Terms", Seventh Edition, IEEE Press, 2000, ISBN SBN 0-7381 -2601 -2
96:
1398:
742:
1688:
694:
565:
There are other factors that affect the range of a two-way radio such as weather, exact frequency used, and obstructions.
68:
2613:
2546:
2392:
1408:
2318:
771:
2412:
1461:
1269:
840:
USFA-TR-099/January 1999, (Emmitsburg, Maryland: U.S. Fire
Administration, 1999) pp. 18-19 and "5.2 Present System,"
801:
708:
677:
472:
115:
75:
2197:
1745:
1547:
189:, and followed by the company's 1943 introduction of the Walkie-Talkie, the best-known example of a two-way radio.
2308:
294:
Scan features are either not used or scan lists are intentionally kept short in emergency applications. Part of
2303:
82:
53:
49:
2634:
2328:
1378:
1221:
2603:
2364:
2261:
1804:
1599:
1571:
1259:
1206:
667:
64:
2593:
2100:
1540:
1428:
1274:
1151:
1034:"8000 Exhibits:Equipment Replacement Costs for a Typical Three Position CDF Command and Control Center,"
175:
1070:
253:
Several portable two-way radios designed for public services (police, fire, rescue) compatible with the
2452:
2374:
2313:
2020:
1466:
904:
For examples, see, Mikhailov, K. E. "Communications
Facilities on the Volga-Moscow Transmission Line,"
700:
737:
418:
life for a communications console used in the
Department of Forestry and Fire Protection is 10 years.
2224:
2185:
2030:
1930:
1859:
1792:
1619:
1491:
1322:
1284:
843:
624:
574:
2583:
1825:
1760:
1713:
1673:
1516:
1332:
629:
182:(TDD) to carry the two directions of the conversation simultaneously on a single radio frequency.
1084:
1038:, (Sacramento, California: State of California, Department of Forestry and Fire Protection, 2006)
2422:
2407:
2251:
2202:
2125:
2025:
1703:
1589:
1584:
1476:
1423:
1226:
42:
2344:
2130:
1945:
1890:
1885:
1698:
1663:
1186:
1144:
1127:
1022:
866:
849:
634:
133:
906:
Long-Distance Electrical Transmission between the V. I. Lenin Hydroelectric Station and Moscow
2246:
2050:
2015:
1935:
1915:
1837:
1725:
1646:
1481:
1039:
167:
16:
Radio that can both transmit and receive a signal, used for bidirectional voice communication
1579:
2160:
2120:
2090:
1847:
1782:
1604:
1486:
1337:
1201:
1196:
852:: Department of General Services, Communications Technology Division, 1982,) pp. V-4 - V-6.
594:
584:
535:
179:
89:
8:
2170:
2110:
1869:
1831:
1629:
1614:
1521:
1368:
1254:
1191:
1057:, (Sacramento, California: State of California EMS Authority, September 2000) pp.38. and
950:
For two examples of drive testing and field measurements of received signal levels, see:
827:
547:
531:
238:
2397:
2354:
2285:
2155:
2085:
2060:
1995:
1842:
1563:
454:
450:
273:
Two-way radio systems can be classified in several ways depending on their attributes.
1095:
2437:
2359:
2273:
2256:
2219:
2065:
1895:
1864:
1730:
1624:
1388:
992:
797:
732:
704:
673:
559:
266:
2105:
2442:
2402:
2382:
2349:
2278:
2236:
2150:
2005:
1990:
1965:
1940:
1900:
1750:
1609:
1594:
1373:
955:
The California Highway Patrol Communications Technology Research Project on 800 MHz
579:
521:
in the US, some frequencies require approval of a frequency coordination committee.
1059:
Arizona Phase II Final Report: Statewide Radio Inter-operability Needs Assessment,
225:
in 1923 by Senior Constable Frederick William Downie of the Victorian Police. The
19:
This article is about two-way radio in general. For hand-held two-way radios, see
2070:
1925:
1693:
1668:
1656:
1506:
1456:
1117:
361:
226:
2268:
2140:
2115:
2075:
2045:
1920:
1755:
1708:
1683:
1641:
1327:
646:
614:
539:
504:
terrain, since radio signals travel differently in forests and urban viewsheds.
485:
393:
140:
2628:
2417:
2190:
2180:
2095:
1985:
1980:
1970:
1955:
1777:
1636:
1342:
1312:
1181:
1112:
356:
20:
767:
2295:
2135:
2080:
2010:
1975:
1910:
1809:
1799:
1651:
1418:
1317:
1307:
641:
619:
543:
261:
202:
197:
186:
171:
2495:
2145:
2055:
2040:
2000:
1960:
1819:
1511:
1501:
1496:
962:
835:
609:
511:
156:
2500:
2207:
1905:
1814:
1770:
1740:
1718:
604:
377:
254:
249:
214:
160:
2485:
1950:
1765:
1532:
1471:
599:
372:
222:
209:
286:
In multi-channel systems, channels are used for separate purposes.
31:
2480:
2470:
2387:
2212:
2035:
1413:
1358:
1279:
1019:
San Rafael Police Radio Committee: Report to Mayor and City Council
863:
San Rafael Police Radio Committee: Report to Mayor and City Council
397:
388:
2475:
2460:
1678:
1433:
1363:
1264:
1211:
908:, (Jerusalem: Israeli Program for Scientific Translations, 1965).
327:
295:
1136:
221:
The first truly mobile two-way radio equipment was developed in
2505:
2465:
1787:
1438:
1403:
1289:
1236:
1231:
1216:
1131:
589:
231:
2490:
2427:
1735:
558:
The useful direct range of a two-way radio system depends on
441:
deal primarily with the United States and do not represent a
153:
144:
A variety of portable handheld two-way radios for private use
1096:"2-Way Radio Range: How Far Can Two-Way Radios Communicate?"
2432:
1004:
For one example, see: "3.2.10.1 Current System Problems,"
989:
Contra Costa County Public Safety Mobile Radio Master Plan
515:
367:
217:
used by firefighters to communicate with their dispatcher
542:. Because this part of the spectrum is heavily used for
507:
the presence of noise, interference, or intermodulation.
400:
mounted in Flightcase, 100% Duty cycle up to 40 W output
136:
communicates with aircraft over a two-way radio headset
1080:
1078:
893:
Special Report: Improving Firefighter Communications,
846:
Communications Technology Research Project on 800 MHz
530:
The most common two-way radio systems operate in the
931:"Spartan Training Bulletin - Volume One – Issue One"
794:
The People's Force, A history of the Victoria Police
1049:
1047:
347:
56:. Unsourced material may be challenged and removed.
1075:
289:
1061:Macro Corporation and The State of Arizona, 2004.
2626:
1044:
917:For an electrocardiogram telemetry example, see
501:local congestion or availability of frequencies.
1055:California EMS Communications Plan: Final Draft
995:: Federal Engineering, Inc., 2002,) pp. 45, 49.
562:conditions, which are a function of frequency.
510:sky wave interference below 50–60 MHz and
489:Two GMRS radios, a hand mic, and two FRS radios
376:Example of control arrangement on a configured
814:IEEE History Milestones retrieved Oct. 2, 2007
762:
760:
276:
1548:
1152:
861:"3.4.1 User Equipment General Deficiencies,"
439:The examples and perspective in this section
421:
414:consoles used elsewhere in the same system.
159:(a radio that can both transmit and receive
2563:Global telecommunications regulation bodies
1006:Trunked Radio System: Request For Proposals
757:
355:systems are designed to perform close to a
2599:
1555:
1541:
1159:
1145:
730:
457:, or create a new section, as appropriate.
953:"Section II: Radio Propagation Studies,"
692:
473:Learn how and when to remove this message
116:Learn how and when to remove this message
1121:) is being considered for deletion. See
669:Modern Dictionary of Electronics, 7th Ed
484:
387:
371:
260:
248:
208:
196:
139:
127:
2627:
1562:
368:Options, duty cycle, and configuration
1536:
1140:
1053:See, "Appendix B - FCC Regulations,"
872:
745:from the original on January 18, 2023
498:government licensing and regulations.
2609:
869:: City of San Rafael, 1995,) pp. 12.
768:"A complete guide to Two-way Radios"
665:
425:
404:
54:adding citations to reliable sources
25:
1025:: City of San Rafael, 1995,) pp. 8.
978:Kenwood TKR-850 specification sheet
659:
13:
774:from the original on June 26, 2022
14:
2646:
1270:Common traffic advisory frequency
1166:
1125:to help reach a consensus. ›
1104:
575:TETRA (Terrestrial Trunked Radio)
525:
2608:
2598:
2589:
2588:
2577:
2198:Free-space optical communication
1071:"VHF or UHF... Which Is Better?"
1040:Adobe PDF file on console costs.
693:Goldsmith, Andrea (8 Aug 2005).
430:
348:Engineered versus not engineered
30:
1089:
1064:
1028:
1011:
998:
981:
972:
944:
923:
911:
898:
881:
328:four-to-twenty milliampere loop
290:Scanning in conventional radios
281:
41:needs additional citations for
1036:8000 Telecommunications Manual
891:use, see "Problem Reporting,"
855:
818:
807:
796:. Melbourne University Press.
786:
731:Hall, Mark (October 3, 2022).
724:
686:
1:
1379:Maritime mobile amateur radio
1110:
770:. Crystal Radio Systems Ltd.
652:
546:and multiple competing uses,
2584:Telecommunication portal
2365:Telecommunications equipment
1522:Voting (diversity combining)
1260:Aircraft emergency frequency
1207:General Mobile Radio Service
7:
2101:Alexander Stepanovich Popov
1275:Mandatory frequency airport
1017:"2.4 Equipment Inventory,"
568:
453:, discuss the issue on the
277:Conventional versus trunked
10:
2651:
1805:Telecommunications history
1467:Automatic vehicle location
834:Special Report: Improving
701:Cambridge University Press
333:
192:
18:
2572:
2514:
2451:
2413:Public Switched Telephone
2373:
2337:
2294:
2235:
2225:telecommunication circuit
2186:Fiber-optic communication
2169:
1931:Francis Blake (telephone)
1878:
1726:Optical telecommunication
1570:
1492:Dynamic range compression
1447:
1409:Dual-tone multi-frequency
1387:
1351:
1323:Professional mobile radio
1298:
1285:Single Frequency Approach
1245:
1174:
844:California Highway Patrol
826:Fundamentals of Tactical
672:. Elsevier. p. 811.
625:Professional Mobile Radio
422:Two-way radio frequencies
380:-capable hand-held radio.
320:
302:
2324:Orbital angular-momentum
1761:Satellite communications
1600:Communications satellite
1517:Radiotelephony procedure
1333:Specialized Mobile Radio
1123:templates for discussion
792:Haldane, Robert. (1995)
666:Graf, Rudolf F. (1999).
630:Specialized Mobile Radio
553:
244:
2203:Molecular communication
2026:Gardiner Greene Hubbard
1855:Undersea telegraph line
1590:Cable protection system
1227:Multi-Use Radio Service
738:Encyclopædia Britannica
696:Wireless Communications
257:digital radio standard
2345:Communication protocol
2131:Charles Sumner Tainter
1946:Walter Houser Brattain
1891:Edwin Howard Armstrong
1699:Information revolution
1299:Land-based commercial
1187:Amateur radio repeater
1023:San Rafael, California
867:San Rafael, California
850:Sacramento, California
635:Mobile radio telephone
490:
401:
381:
270:
258:
218:
206:
145:
137:
134:air traffic controller
2319:Polarization-division
2051:Narinder Singh Kapany
2016:Erna Schneider Hoover
1936:Jagadish Chandra Bose
1916:Alexander Graham Bell
1647:online video platform
1301:and government mobile
1248:(aeronautical mobile)
488:
391:
375:
264:
252:
212:
200:
168:simplex communication
143:
131:
2635:Radio communications
2161:Vladimir K. Zworykin
2121:Almon Brown Strowger
2091:Charles Grafton Page
1746:Prepaid mobile phone
1674:Electrical telegraph
1338:Trunked radio system
1202:Public Radio Service
1197:Family Radio Service
1175:Amateur and hobbyist
595:Family Radio Service
585:Digital Mobile Radio
451:improve this section
180:time-division duplex
50:improve this article
2111:Johann Philipp Reis
1870:Wireless revolution
1832:The Telephone Cases
1689:Hydraulic telegraph
1369:Coast radio station
1255:Air traffic control
1192:Citizens band radio
1085:Two Way Radio Range
828:Command and Control
548:spectrum management
239:Bayonne, New Jersey
213:Two-way radio in a
2309:Frequency-division
2286:Telephone exchange
2156:Charles Wheatstone
2086:Jun-ichi Nishizawa
2061:Innocenzo Manzetti
1996:Reginald Fessenden
1731:Optical telegraphy
1564:Telecommunications
1352:Marine (shipboard)
1237:UHF CB (Australia)
887:For an example of
491:
402:
392:Motorola MOTOTRBO
382:
271:
259:
219:
207:
146:
138:
2622:
2621:
2360:Store and forward
2355:Data transmission
2269:Network switching
2220:Transmission line
2066:Guglielmo Marconi
2031:Internet pioneers
1896:Mohamed M. Atalla
1865:Whistled language
1530:
1529:
1391:Selective calling
993:Fairfax, Virginia
965:Technical Journal
560:radio propagation
483:
482:
475:
405:Life of equipment
126:
125:
118:
100:
2642:
2612:
2611:
2602:
2601:
2592:
2591:
2582:
2581:
2580:
2453:Notable networks
2443:Wireless network
2383:Cellular network
2375:Types of network
2350:Computer network
2237:Network topology
2151:Thomas A. Watson
2006:Oliver Heaviside
1991:Philo Farnsworth
1966:Daniel Davis Jr.
1941:Charles Bourseul
1901:John Logie Baird
1610:Data compression
1605:Computer network
1557:
1550:
1543:
1534:
1533:
1448:System elements
1374:Marine VHF radio
1161:
1154:
1147:
1138:
1137:
1098:
1093:
1087:
1082:
1073:
1068:
1062:
1051:
1042:
1032:
1026:
1015:
1009:
1002:
996:
985:
979:
976:
970:
948:
942:
941:
939:
937:
927:
921:
915:
909:
902:
896:
885:
879:
876:
870:
859:
853:
822:
816:
811:
805:
790:
784:
783:
781:
779:
764:
755:
754:
752:
750:
733:"Motorola, Inc."
728:
722:
721:
719:
717:
690:
684:
683:
663:
580:Astro (Motorola)
478:
471:
467:
464:
458:
434:
433:
426:
269:radio in a truck
121:
114:
110:
107:
101:
99:
58:
34:
26:
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2510:
2447:
2369:
2333:
2290:
2239:
2231:
2172:
2165:
2071:Robert Metcalfe
1926:Tim Berners-Lee
1874:
1694:Information Age
1566:
1561:
1531:
1526:
1507:Rayleigh fading
1449:
1443:
1390:
1383:
1347:
1300:
1294:
1247:
1241:
1170:
1165:
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1101:
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1076:
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1065:
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999:
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916:
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903:
899:
886:
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877:
873:
860:
856:
838:Communications,
830:: A Soviet View
823:
819:
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808:
791:
787:
777:
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766:
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758:
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746:
729:
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195:
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65:"Two-way radio"
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2141:Camille Tissot
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2116:Claude Shannon
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2106:Tivadar Puskás
2103:
2098:
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2076:Antonio Meucci
2073:
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2046:Charles K. Kao
2043:
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2023:
2021:Harold Hopkins
2018:
2013:
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1860:Videotelephony
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1450:and principles
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615:Motorola Saber
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540:radio spectrum
527:
526:UHF versus VHF
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445:of the subject
443:worldwide view
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2096:Radia Perlman
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2012:
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1989:
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1986:Lee de Forest
1984:
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1981:Thomas Edison
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1971:Donald Davies
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1956:Claude Chappe
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1778:Semiconductor
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1343:Walkie-talkie
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1182:Amateur radio
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1168:Two-way radio
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1128:Two-Way_Radio
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802:0-522-84674-2
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710:9780521837163
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679:9780080511986
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541:
538:parts of the
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477:
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365:
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358:
357:specification
354:
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331:
329:
314:
310:
309:
308:
300:
297:
287:
274:
268:
263:
256:
251:
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240:
237:In 1933, the
235:
234:patrol cars.
233:
228:
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204:
199:
190:
188:
183:
181:
177:
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150:two-way radio
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120:
117:
109:
98:
95:
91:
88:
84:
81:
77:
74:
70:
67: –
66:
62:
61:Find sources:
55:
51:
45:
44:
39:This article
37:
33:
28:
27:
22:
21:Walkie-talkie
2296:Multiplexing
2171:Transmission
2136:Nikola Tesla
2126:Henry Sutton
2081:Samuel Morse
2011:Robert Hooke
1976:Amos Dolbear
1911:John Bardeen
1830:
1810:Telautograph
1714:Mobile phone
1669:Edholm's law
1652:social media
1585:Broadcasting
1429:Quik-Call II
1419:Push-to-talk
1389:Signaling /
1318:Mobile radio
1308:Base station
1167:
1116:
1091:
1066:
1058:
1054:
1035:
1030:
1018:
1013:
1005:
1000:
988:
983:
974:
961:
954:
946:
934:. Retrieved
925:
918:
913:
905:
900:
892:
888:
883:
874:
862:
857:
848:, 80-C477, (
841:
833:
825:
820:
809:
793:
788:
776:. Retrieved
747:. Retrieved
736:
726:
714:. Retrieved
695:
688:
668:
661:
642:Police radio
620:Mobile radio
564:
557:
544:broadcasting
529:
512:tropospheric
492:
469:
463:October 2012
460:
440:
416:
412:
408:
396:DR3000 with
383:
352:
351:
340:
337:
324:
306:
293:
285:
282:Conventional
272:
236:
220:
203:marine radio
187:World War II
184:
172:push-to-talk
165:
149:
147:
112:
103:
93:
86:
79:
72:
60:
48:Please help
43:verification
40:
2496:NPL network
2208:Radio waves
2146:Alfred Vail
2056:Hedy Lamarr
2041:Dawon Kahng
2001:Elisha Gray
1961:Yogen Dalal
1886:Nasir Ahmed
1820:Teleprinter
1684:Heliographs
1512:Tone remote
1502:Link budget
1497:Fade margin
1424:Quik-Call I
1111:‹ The
963:Bell System
936:October 18,
889:talk around
836:Firefighter
778:January 17,
749:January 17,
610:Quik Call I
514:bending at
341:acknowledge
176:full-duplex
161:radio waves
157:transceiver
2542:Antarctica
2501:Toasternet
2423:Television
1906:Paul Baran
1838:Television
1822:(teletype)
1815:Telegraphy
1793:transistor
1771:Phryctoria
1741:Photophone
1719:Smartphone
1709:Mass media
1222:Mobile rig
653:References
605:Project 25
353:Engineered
316:frequency.
255:Project 25
215:fire truck
76:newspapers
2526:Americas
2515:Locations
2486:Internet2
2247:Bandwidth
1951:Vint Cerf
1848:streaming
1826:Telephone
1766:Semaphore
1657:streaming
1482:DC remote
1472:Call sign
1246:Aviation
600:GE Marc V
455:talk page
265:A mobile
223:Australia
205:on a ship
106:July 2022
2629:Category
2594:Category
2481:Internet
2471:CYCLADES
2388:Ethernet
2338:Concepts
2262:terminal
2213:wireless
2036:Bob Kahn
1879:Pioneers
1704:Internet
1595:Cable TV
1487:Dispatch
1414:MDC-1200
1359:2182 kHz
1280:MULTICOM
1113:template
772:Archived
743:Archived
716:20 April
569:See also
449:You may
398:duplexer
394:Repeater
362:antennas
2614:Commons
2604:Outline
2557:Oceania
2476:FidoNet
2461:ARPANET
2274:circuit
1843:digital
1572:History
1457:Antenna
1434:Selcall
1364:500 kHz
1265:Airband
1212:KDR 444
1115:below (
334:Digital
193:History
90:scholar
2552:Europe
2522:Africa
2506:Usenet
2466:BITNET
2403:Mobile
2279:packet
1788:MOSFET
1783:device
1580:Beacon
1439:SELCAL
1404:D-STAR
1290:UNICOM
1232:PMR446
1217:LPD433
1132:Curlie
1118:Curlie
804:, 1995
800:
707:
676:
590:PMR446
321:Analog
303:Duplex
232:Lancia
132:Naval
92:
85:
78:
71:
63:
2535:South
2530:North
2491:JANET
2428:Telex
2418:Radio
2257:Nodes
2252:Links
2173:media
1751:Radio
1736:Pager
1664:Drums
1630:video
1625:image
1615:audio
1399:CTCSS
554:Range
245:Types
154:radio
152:is a
97:JSTOR
83:books
2547:Asia
2433:UUCP
2393:ISDN
1462:APRS
938:2017
842:The
798:ISBN
780:2023
751:2022
718:2016
705:ISBN
674:ISBN
534:and
312:use.
201:VHF
69:news
2438:WAN
2408:NGN
2398:LAN
1679:Fax
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