SmartTrunk Systems SmarTrunk II, Обзор системы, Страница: 54 / 57

System Overview
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Selective Calling
One of the key features of the SmarTrunk II system is the ability to
make private calls to another mobile user. Unlike many LTR systems,
all SmarTrunk II users are identified with an individual subscriber
number as well as a group subscriber number. When using a radio with
a DTMF keypad, a SmarTrunk II user can selectively call other users in
his group or fleet by entering the mobile’s subscriber number followed
by a routing code, very similar to dialing a cellular phone.
Telephone Interconnect
The ability to make telephone interconnect calls is also a standard
feature of SmarTrunk II. Each radio equipped with a DTMF keypad
(and even some radios without keypads) can be used as a mobile
telephone. Like private calls, the dialing procedure is very similar to
using a cellular phone. And the telephone interconnect circuitry is built-
in to every SmarTrunk II controller at no extra cost.
On the other hand, many LTR controllers are designed only for basic
dispatch operation, so that telephone interconnect is an expensive
option. On the mobile side, each subscriber who is authorized to make
telephone interconnect calls must have an extra ID code assigned,
which again squanders the limited ID codes available in the LTR
scheme.
Converting Conventional Systems
All 800 MHz trunking systems, including LTR, were designed for new
systems on clear (exclusive) channels, using dedicated mobile and
portable radio equipment. Below 800 MHz, however, the environment
in most countries is quite different. VHF and UHF channels are
already crowded with conventional users, and there may be two or more
repeaters in the same service area operating on the same frequency.
This means that in order to establish a trunked radio system at these
frequencies, it is necessary to
gradually convert existing community
repeater systems from conventional to trunked operation.
Appendix C • SmarTrunk vs. LTR