Trunking Concepts

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Trunking Concepts
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PARTY LINES
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The Next Generation
Sarah, get me the courthouse.
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TRUNKING
The sharing of a small number of radio channels
between a large number of users
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Voice Channels
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Individual users can be combined into collections
called
Talkgroups
They are made up of a
.
collection of users who typically need to
communicate in order to accomplish their job.
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Talkgroup
Talkgroup
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Trunked Communication System

• Compare a trunked communication system to the
• system many airlines use.
• Any agent can handle a transaction for
• any user.
• Each user is handled by the next available
• ticket agent.

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If there are more users than ticket agents, a
single queue builds up. The single queue gives
all users equal access to the available ticket
agents.

• It is improbable that a large percentage of users
• will want to make a call at the same time.
• Most conversations are relatively short.

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A Motorola trunked radio system also uses a

that functions like a traffic
officer and controls the operation of the
trunked repeaters.
central controller
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Trunking Infrastructure

• A series of trunked repeaters

• Operation and Assignment of the Control
• Channel

- Who? - What? - Where?
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Call Processing Event Sequence
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Step 1
Central Controller Receives a Call Request
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Step 2
The central controller assigns one of the
idle repeaters to the users talkgroup. In this
case, Repeater 5 is assigned.
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Step 3
All radios monitoring the control channel
receive the transmitted message.
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Step 4
All of those radios assigned to the
talkgroup associated with the Talkgroup ID switch
to the assigned voice channel frequency.
Voice
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Step 5
When the call is completed, the radios in the
talkgroup switch back to the control channel
frequency. The previously assigned voice
channel now becomes available for other calls.
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Site Trunking
The Prime Site has lost communication to the
central controller.
Radios operate as they would in a normal trunking
environment, except, if there are other entity
sites in your system, the radio user will not be
able to communicate with radios that have roamed
outside their home system. Communication with
your dispatch center may be limited. The radio
may be programmmed to emit a tone every 6
seconds. NOTE Multiple individual sites one
site for site trunking
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Failsoft
Major Failures - Central Controller - All Four
Control Channels - All Voice Channels

• Radios operate as they would on a conventional
• repeater system
• Low level alert tone every 10 seconds