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Trunking Operation
codes in the ID memory (see “Storing Talk Group IDs”
on Page 55). To listen to the transmission, the mode of
the programmed channel must be the same as that of
the trunking channel (LT, MO, or ED).
When an ID code is received, the ID list for the bank is
searched, and if found, the text name stored for the ID
appears. If not found, scanning resumes immediately
unless the bank is in open trunking mode.
Note:
There might be more than one talk group transmit-
ting at a time in some Motorola trunking systems. If you
set the scanner to manually tune in Motorola trunking
mode, you will hear the talk group on that channel, but
the display will alternate between all active IDs.
Trunking group frequencies are included in the supplied
Police Call Trunking Guide
. Frequency fleet map and
talk group information is also widely available on the In-
ternet, at
www.trunkscanner.com
for example.
UNDERSTANDING TRUNKING
In the past, groups that transmit frequently, such as po-
lice departments, could transmit on only a few frequen-
cies. This resulted in heavy traffic and often required 2-
way radio users to wait for a specific frequency to clear
before transmitting. Trunked systems allow more groups
of 2-way radio users to use fewer frequencies. Instead of
selecting a specific frequency to transmit on, a trunked
system chooses one of several frequencies when the 2-
way radio user transmits. The system automatically
transmits the call on that frequency, and also sends a
code that identifies that 2-way radio user’s transmission
on a control channel.
This scanner lets you easily hear both the call and re-
sponse transmissions for that 2-way radio user and
therefore follow the conversation. For EDACS and Motor-
ola (above 806 MHz range), the scanner monitors the
control channel between each transmission to identify talk
groups. For some Motorola (under 512 MHz range) and
LTR systems, the scanner uses the subaudible data sent
with each transmission to identify talk groups.
20-522b.fm Page 49 Thursday, September 7, 2000 9:41 AM