170:
The fleetmap lays out the various talkgroups that the agency requires to successfully undertake its business. For example, in an ambulance service fleetmap there will be a talkgroup created for each of the hospital ER's that the ambulances interact with; talkgroups for communications with dispatch(s), talkgroups for special events or disasters, a talkgroup for air medical transport, and a number of talkgroups that are shared (with appropriate controls) with other first response agencies such as police and fire services. Each talkgroup is assigned a unique digital ID on the system so that the controller can direct transmissions to the radios which are intended to receive them. Within the same shared system there can be a fleet of ambulances, a fleet of police users, and a fleet of firefighters. In most shared public safety/public service systems, whether city-wide, or state/province-wide, there are often additional users sharing the system at a pre-determined lower priority for service such as animal control, public works, highways maintenance, correctional services, natural resources, etc. The system may also include talkgroups for federal agencies operating within the jurisdiction and in some cases commercial users which provide assistance to general public safety. These fleetmaps are considered subfleets of the actual talkgroups. The subfleets are intuitively programmed into the users' radios so that the users can easily find a talkgroup when s/he is required to switch for a particular situation. Alternatively, a trunking system dispatch console operator can actually 'patch' two talkgroups together making a new 'virtual' talkgroup to allow users from different agencies to communicate without having to switch channels.
62:) with mobile and portable two-way radios communicate over a single shared radio channel, with one user at a time talking. These systems typically have access to multiple channels, up to 40-60, so multiple groups in the same area can communicate simultaneously. In a conventional (non-trunked) system, channel selection is done manually; before use, the group must decide which channel to use, and manually switch all the radios to that channel. This is an inefficient use of scarce radio channel resources because the user group must have exclusive use of their channel regardless of how much or how little they are transmitting. There is also nothing to prevent multiple groups in the same area from choosing the same channel, causing conflicts and 'cross-talk'. A trunked radio system is an advanced alternative in which the channel selection process is done automatically, so as to avoid channel conflicts and maintain frequency efficiency across multiple talkgroups. This process is handed by what is essentially a central
174:
and a fire service block on the same system might begin with 102200 up to 102299. This identifies the system as 102XXX and provides one hundred talkgroup ID's for each agency. Agency-shared talkgroups (sometimes referred to as Mutual Aid or Inter-agency) may be assigned a block starting at 102500 up to 102520, allowing for twenty shared talkgroups that can be offered for use by any authorized agency. In many province-wide systems, it is mandatory for participation in the system for user agencies to include all of the authorized shared talkgroups and/or shared simplex frequencies.
74:. When any user in that group wishes to communicate with another user in the talkgroup, an idle radio channel is found automatically by the system and the conversation takes place on that channel. Many unrelated conversations can occur on a channel, making use of the otherwise idle time between conversations. Each radio transceiver contains a microprocessor that handles the channel selection process. A control channel coordinates all the activity of the radios in the system. The control channel computer sends packets of data to enable one
31:
204:
the telephone and radio systems. In both cases once the trunking capacity of the systems is fully used, all subsequent users will receive a busy signal. In such a case management of communications becomes critical with only very local communications sharing simplex (non-system) frequencies, and longer distance communications sharing pre-planned trunking talkgroups and governing use of the resources to essential communications.
132:— to request communication on a specific talkgroup. The controller sends a signal to all radios monitoring that talkgroup, instructing the radios to automatically switch to the frequency indicated by the system to monitor the transmission. After the user is done speaking, the users' radios return to monitoring the control channel for additional transmissions.
228:
Trunked radio takes advantage of the probability that with any given number of users, not everyone will need channel access at the same time, therefore fewer discrete radio channels are required. From another perspective, with a given number of radio channels, a much greater number of user groups can
219:
For example, if police communications are configured in such a way that twelve conventional channels are required to permit citywide dispatch based upon geographical patrol areas, during periods of slow dispatch activity, much of that channel capacity is idle. In a trunked system, the police units in
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Generally in planning a multi-agency trunking radio system, each agency is assigned a 'block' of talkgroup ID numbers based on the number of talkgroups they anticipate requiring, plus some excess for future expansion. Thus a police service block of talkgroup ID's might begin with 102100 up to 102199,
232:
To the user, a trunking radio looks just like an 'ordinary' radio: there is a 'channel select switch' for the user to select the 'channel' that they want to use. In reality though, the 'channel switch' is not switching frequencies as in a conventional radio but when changed, it refers to an internal
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area used by crop harvesting crews may overload and experience busy signals during peaks in harvesting. A system used by a ski resort may overload on a holiday weekend. Disaster planning experts like to say that trunked system users are likely to hear busy signals for the first time when a disaster
169:
Each system is built with a number of system talkgroups identified as required by the planned user agencies, to which new talkgroups can easily be added as the system matures and new agencies or new requirements are identified. For each user agency, talkgroups are assigned in an agency 'fleetmap'.
621:
SMR systems are not designed and built to the same standards as government trunked systems used to manage emergencies. There are many documents addressing this issue. One article discussing this topic is, "Intra- and Inter-County
Coordination and Interoperability: Existing Cooperative Agreements,"
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These systems exhibit some of the characteristics of a high tier trunked radio system but not all features. Therefore, they are suitable for small deployments where users are expected to use the entire network available (such as a private system covering a campus or town). Because of their lack of
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This concept has been simply applied to radio user groups, to determine the optimal number of channels needed, under normal conditions, to accommodate a given number of users. In the event of a widespread emergency such as a major earthquake, many more users than normal will attempt to access both
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Most scanners that can listen to trunked radio systems (called trunk tracking) are able to scan and store individual talkgroups just as if they were frequencies. The difference in this case is that the groups are assigned to a certain bank in which the trunked system is programmed. In other words,
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These systems are relatively simple in their operation and only meet the minimum requirements to be defined as a 'trunked' radio system. They generally do not have enhanced features such as data communications or registration awareness. They will provide simple trunking facilities for voice calls
69:
Trunking is a more automated and complex radio system, but provides the benefits of less user intervention to operate the radio and greater spectral efficiency with large numbers of users. Instead of assigning a radio channel to one particular user group at a time, users are instead assigned to a
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The concept of trunking (resource sharing) is actually quite old, and is taken from telephone company technology and practice. Consider two telco central office exchanges, one in town "A" and the other in adjacent town "B". Each of these central offices has the theoretical capacity to handle ten
216:'Trunked' radio systems differ from 'conventional' radio systems in that a conventional radio system uses a dedicated channel (frequency) for each individual group of users, while 'trunking' radio systems use a pool of channels which are available for a great many different groups of users.
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In SMR systems, many factors affect the quality of service. This may include the capacity of the radio system versus the number of radio units using the system. A talkative user community may cause busy signals while a disciplined, professional group of SMR users may keep channels idle.
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be accommodated. In the example of the police department, this additional capacity could then be used to assign individual talkgroups to specialized investigative, traffic control, or special-events groups which might otherwise not have the benefit of individual private communications.
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DMR/dPMR true Tier 3/Mode 3 protocols are intended eventually to migrate into the "Advanced Mature high end" list below but today (2015) cannot be classified as such due to major interoperability issues, lack of mature protocol and lack of clearly defined user interface protocol.
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software program which causes a new talkgroup affiliation to be transmitted on the control channel. This identifies the specific radio to the system controller as a member of a specific talkgroup, and that radio will then be included in any conversations involving that talkgroup.
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coordinates the system so talkgroups can share these frequencies seamlessly. The purpose is to dramatically increase system capacity with optimal use of frequencies. Many radios today treat talkgroups as if they were frequencies, since they behave like such. For example, on a
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If all 10,000 subscribers in "A" were to simultaneously call 10,000 subscribers in "B", then it would be necessary to have 10,000 lines to connect the two towns. However, the odds of that happening are remote, as the number of simultaneous phone calls is usually much lower.
607:
The date is unclear. The FCC web site has a page under the
Wireless Telecommunication Bureau defining Specialized Mobile Radio Service. It claims licenses were first issued in 1979. Another publication suggests licenses were first issued in 1976. See: "3.6.1 Overview,"
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should overlook the desired coverage area. Federal
Communications Commission regulations require systems using the same radio frequency to be spaced 70 miles from one another or do an engineering study to confirm there will be no interference from closer spacing.
337:. This is a measurement of the sound quality over all of the involved pieces of communications equipment from end to end. The first clue this may be an issue is that radio users with normal hearing have trouble understanding others when speaking over the radio.
135:
This arrangement allows multiple groups of users to share a small set of actual radio frequencies without hearing each other's conversations. Trunked systems primarily conserve limited radio frequencies and also provide other advanced features to users.
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This also allows great flexibility in radio usage – the same radio model can be used for many different types of system users (i.e. Police, Fire, Public Works, Animal
Control, etc.) simply by changing the software programming in the radio itself.
34:
A central-controlled trunked system uses a control channel (as shown). Another type, scan based trunked systems, (not shown) do not have a control channel. Frequencies are for discussion purposes and do not correspond to any specific
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Since the talkgroups are constantly transmitting on different frequencies, trunked radio systems makes it more difficult for a scanner listener without a programmed trunk tracking scanner to keep up with the conversation.
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In our example of police dispatch, different talkgroups are assigned different system priority levels, sometimes with 'preemption' capability, attempting to ensure that communication between critical units is maintained.
105:, or other entity. A secondary benefit of a trunking radio system is the ease with which it can accommodate radio interoperability and with proper planning, add authorized user agencies to the system post-implementation.
260:
This is not designed to be a list of manufacturers' equipment types, it is intended as a list of air protocol types unless significant vendor specific modifications have been made which violate the published standard.
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Maintenance practices also can affect quality. In some systems, the operator may remove one channel of a trunked system from service to perform repairs. In a heavily used system, this could cause busy signals.
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from the
Department of Homeland Security analyzes and compares conventional, trunked, and hybrid LMR systems and provides high-level definitions of the architecture alternatives associated with each option.
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thousand individual telephone numbers. (Central office "A", with prefix "123", has available 10,000 numbers from 123-0000 to 123-9999; central office "B", with prefix "124", the same.)
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regulations. The term is of US regulatory origin but may be used in other regions to describe similar commercial systems which offer a radio communications service to businesses.
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a given geographical area are not assigned a dedicated channel, but instead are members of a talk-group entitled to draw upon the common resources of a smaller pool of channels.
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Trunked radio technologies today have generally diverged into three distinct types or 'tiers'. These are not 'official', but are clearly defined within protocol types:-
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The primary purpose of this type of system is efficiency; many people can carry many conversations over only a few distinct frequencies. Trunking is used by many
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SMRs were created when the
Federal Communications Commission began to license business and commercial 800 MHz two-way radio systems in the late 1970s.
511:
Common Air
Interface (CAI) was accepted at the meeting of the ITU-R (International Telecommunication Union Radiocommunications Sector) held in November
519:, published in February 2017. It is an open, multi-vendor protocol widely adopted in mission-critical applications in Japan, USA and mainland Europe.
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system, operated by a service in the VHF, 220, UHF, 700, 800 or 900 MHz bands. Some systems with advanced features are referred to as an
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it is very common to be able to assign talkgroups into banks or lock them out, exactly like that of conventional frequencies.
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US Patent and
Trademark Office Registration Number 2407576, Serial Number 75400608, registered to Uniden America Corporation.
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occurs. A major flood or earthquake is likely to generate a level of call traffic that loads the system to capacity.
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compatible with trunked systems appeared on the market. One of the first companies to bring these devices to market,
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computer network. Users' radios send data packets to a computer, operating on a dedicated frequency — called a
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advanced features they generally are not suited to mission critical deployments, public access mobile radio (
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is a common formula that predicts the optimal number of trunk lines actually needed under normal conditions.
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Contra Costa County Public Safety Mobile Radio Master Plan, Final Report, June 18, 2002,
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A 'talkgroup' is an assigned logical group of users on a trunked radio system. Unlike a
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Talk groups, scanning, and group calls are defined in, "Section 2: Needs
Summary,"
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Arizona Phase II Final Report: Statewide Radio
Interoperability Needs Assessment,
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Engineering documentation for these systems suggests another evaluation would be
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612:(Phoenix, Arizona: Macro Corporation and The State of Arizona, 2004) pp. 30.)
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Some systems experience seasonal peaks. For example, a trunked system in an
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Some trunked radio protocols provide additional reliability and security.
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See External link: Federal Communications Commission definition of
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252:, trademarked the term 'trunk tracking' on December 5, 1997.
626:(Fairfax, Virginia: Federal Engineering, Inc., 2002) pp. 25.
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system that uses a control channel to automatically assign
574:"Conventional and Trunked Radio Systems Comparison Report"
66:, a function automatically handled by a computer system.
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Macro Corporation and The State of Arizona, 2004, pp. 16.
446:) type operation or uncoordinated shared user types.
294:). Specialized Mobile Radio is a term defined in US
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644:FCC PDF file describing US private radio services.
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321:Siting of the system affects coverage: the system
490:, Motorola Capacity Plus, Motorola Connect Plus
183:the talkgroups are stored on the trunked bank.
911:
664:
8:
93:and other municipal services, who all share
639:FCC definition of Specialized Mobile Radio.
479:Icom IDAS Digital trunked Land Mobile Radio
212:Differences from conventional two-way radio
78:to talk together, regardless of frequency.
51:to groups of user radios. In a traditional
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124:In essence, a trunked radio system is a
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296:Federal Communications Commission (FCC)
476:Kenwood NEXEDGE Digital trunked radio
496:(integrated Digital Enhanced Network)
85:to provide two-way communication for
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187:Comparison with telephone trunking
25:
1029:Common traffic advisory frequency
288:Enhanced Specialized Mobile Radio
279:) may be an analog or digital
256:Types of trunked radio systems
148:which assigns users a certain
1:
1138:Maritime mobile amateur radio
832:General Electric Mobile Radio
1281:Voting (diversity combining)
1019:Aircraft emergency frequency
966:General Mobile Radio Service
1034:Mandatory frequency airport
1328:
1226:Automatic vehicle location
727:Type II SmartZone OmniLink
431:Type II SmartZone OmniLink
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1307:Radio resource management
1251:Dynamic range compression
1168:Dual-tone multi-frequency
1082:Professional mobile radio
1044:Single Frequency Approach
867:LTR Standard and Passport
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522:Other protocols include:
515:and it has been added to
391:LTR Standard and Passport
1276:Radiotelephony procedure
1092:Specialized Mobile Radio
273:Specialized Mobile Radio
268:Specialized Mobile Radio
64:radio traffic controller
56:land mobile radio system
18:Specialized mobile radio
986:Multi-Use Radio Service
335:delivered audio quality
109:Principles of operation
27:Class of a radio system
1058:Land-based commercial
946:Amateur radio repeater
224:Advantages of Trunking
36:
1302:Trunked radio systems
1060:and government mobile
1007:(aeronautical mobile)
680:Trunked radio systems
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1097:Trunked radio system
961:Public Radio Service
956:Family Radio Service
934:Amateur and hobbyist
70:logical grouping, a
58:a group of users (a
41:trunked radio system
1128:Coast radio station
1014:Air traffic control
951:Citizens band radio
849:Logic Trunked Radio
825:distributed control
376:Logic Trunked Radio
83:government entities
1111:Marine (shipboard)
996:UHF CB (Australia)
691:Central controller
305:Quality of service
165:Fleet maps and IDs
146:conventional radio
49:frequency channels
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16:(Redirected from
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159:radio scanner
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115:Erlang (unit)
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45:two-way radio
42:
32:
19:
1188:Quik-Call II
1178:Push-to-talk
1148:Signaling /
1096:
1077:Mobile radio
1067:Base station
872:LTR MultiNet
862:LTR Passport
857:LTR Standard
823:Scan-based /
679:
623:
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521:
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448:
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396:LTR MultiNet
386:LTR Passport
381:LTR Standard
344:
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315:agricultural
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1271:Tone remote
1261:Link budget
1256:Fade margin
1183:Quik-Call I
356:Ericsson GE
341:Entry-level
53:half-duplex
1296:Categories
981:Mobile rig
140:Talkgroups
113:See also:
1241:DC remote
1231:Call sign
1005:Aviation
839:GE Marc V
371:GE Mark V
351:SmarTrunk
244:In 1997,
150:frequency
76:talkgroup
72:talkgroup
60:talkgroup
1246:Dispatch
1173:MDC-1200
1118:2182 kHz
1039:MULTICOM
806:Tier III
783:TETRAPOL
768:MPT-1327
542:TETRAPOL
527:MPT-1327
488:Motorola
473:Tier III
437:Standard
406:Motorola
323:antennas
198:Erlang-B
178:Scanning
95:spectrum
1216:Antenna
1193:Selcall
1123:500 kHz
1024:Airband
971:KDR 444
877:LTR-Net
773:OpenSky
712:Type II
416:Type II
401:LTR-Net
281:trunked
35:system.
1198:SELCAL
1163:D-STAR
1049:UNICOM
991:PMR446
976:LPD433
795:Mode 3
707:Type I
598:below.
483:Hytera
467:Mode 3
411:Type I
346:only.
250:Uniden
103:county
91:police
1158:CTCSS
778:TETRA
758:EDACS
741:Other
548:Notes
532:TETRA
366:EDACS
43:is a
1221:APRS
799:NXDN
793:dPMR
788:GoTa
732:iDEN
513:2016
509:NXDN
494:iDEN
465:dPMR
444:PAMR
292:ESMR
99:city
1236:CAD
810:PDT
804:DMR
596:SMR
471:DMR
277:SMR
1298::
101:,
89:,
39:A
919:e
912:t
905:v
672:e
665:t
658:v
290:(
275:(
20:)
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