SmartTrunk Systems SmarTrunk II, System Overview, Page: 53 / 57

Operating in a Crowded VHF and UHF Environment
In an LTR system, the subscriber radio must receive instructions from
its home channel before it can initiate a call. As a result, any home
channels must be assigned to clear channels. Otherwise, whenever a
co-channel user is on the air, all radios assigned to that home channel
will be unable to receive instructions and, consequently, unable to
initiate or receive calls of any kind.
Since the VHF and UHF spectrum is heavily populated in many
countries, obtaining a clear channel may not be an option. With
SmarTrunk II, all of the channels in the system may be shared with co-
channel users since all the mobiles in the system automatically
monitor for a foreign carrier before selecting a channel. As a result,
SmarTrunk II is much better equipped to operate in a crowded RF
environment than LTR.
System Security Considerations
One of the primary concerns of system operators is maintaining system
security against hackers, pirates, and other unauthorized users. LTR
relies on a sub-audible data stream that is easily monitored and
duplicated. Many radio service monitors have the ability to read LTR
codes over the air, so that an unscrupulous dealer can easily determine
valid LTR codes. Once the LTR codes are determined, unauthorized
radios can be easily programmed and loaded on a system without the
knowledge or consent of the system operator.
By comparison, SmarTrunk II employs a highly encrypted, in-band
proprietary digital data burst which is immune to hackers and pirates.
As a “closed” system which can be accessed only by authorized users,
SmarTrunk II provides the system operator very high security against
non-paying customers and other unauthorized users. And if a radio
should ever become lost or stolen, it can be remotely disabled without
affecting the rest of the group or fleet.
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SmarTrunk Systems, Inc.
System Overview