SmartTrunk Systems SmarTrunk II, System Overview, Page: 39 / 57

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SmarTrunk Systems, Inc.
SECTION 7
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Frequently Asked Questions
Q. What is SmarTrunk II?
The SmarTrunk II Digital Trunking System is a reasonably priced, wireless
communications system which supports group dispatch, individual selective
calling and telephone interconnect applications. It is widely used for applications
below 800 MHz, with over 6,000 systems and 500,000 subscribers in over 98
counties worldwide. By relying on low cost, conventional radio equipment and
add-on logic boards, SmarTrunk II is able to offer many advanced features
typically found in much higher cost systems.
Q. How does SmarTrunk II differ from other trunking formats?
The most recent FCC interpretation of “trunking” found in the Part 88 rules uses
the word “centralized” to described a trunking system which utilizes a dedicated
control channel to provide mobile control. Since the SmarTrunk system does not
utilize a dedicated control channel, we have chosen to call SmarTrunk II a
“decentralized” or “Scan-Based” system.
Because there is no central controller required, SmarTrunk II is generally much
less expensive and easier to license than centralized trunking systems.
Q. What is a “Scan Based” system?
Unlike centralized systems, scan based systems do not require exclusive RF
channels. The channel selection intelligence is located in the mobiles. When a
subscriber initiates a call, the mobile unit searches for a clear channel based on
the absence of either system CTCSS tone or carrier. When a clear channel is
located, the mobile unit places a request for service. After validating the
subscriber’s ID, the channel controller completes the connection and provides a
talk path for the duration of the call.
Q. How are incoming calls processed?
When the mobile unit is in an idle condition, the receive audio and the PTT
functions are disabled. During this time the mobile is scanning for a system “call
collect” tone. When the call collect tone is detected, the mobiles stops scanning
and listen for it’s correct digital data pack. When the correct data pack is
detected, the receive audio and the PTT function is enabled and normal radio
operation begins. All unadressed radio’s resume scanning . At the end of the
call the repeater disconnects and the mobiles that were communicating resume
scanning.
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