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TRUNK SCANNING
Your scanner is designed to track
transmissions on Motorola Type I,
Type II, GE/Ericsson EDACS, and hy-
brid analog trunking systems. Re-
member these important points when
tracking transmissions:
• Your scanner monitors Type II
systems by default. However, you
can change this if the system in
your area is different (see “Types
of Trunking Systems” on this page
and “Scanning Type I and Hybrid
Trunked Systems” on Page 40 for
more information).
• Your scanner tracks a trunked
system
or
scans frequencies in
conventional mode, but it cannot
do both at the same time.
• The frequencies for many of the
800 MHz public safety systems
are listed in the separate “National
Public Safety Trunked System
Frequency & Talk Group Guide”
included with this scanner.
TYPES OF TRUNKING
SYSTEMS
Your trunk scanning scanner can
monitor three basic types of systems
—
Type I
,
Type II, and EDACS
. In-
stead of selecting a specific frequency
to transmit on, a trunked system
chooses one of several frequencies in
a 2-way radio user’s talk group when
that user presses PTT (push to talk).
Thus, trunking systems allocate a few
frequencies among many different us-
ers, but the way Type I and Type II
systems do this is slightly different.
One important distinction between
these systems is the amount of data
transmitted by each radio when its
PTT button is pressed. In a Type I
system, the radio’s talk group ID and
its current affiliation (the trunk system
it belongs to) are both transmitted. In a
Type II system, only the radio’s talk
group ID is transmitted.
Why the difference? In Type I sys-
tems, each radio in the trunk group in-
dividually transmits its own affiliation,
while the trunk system maintains a da-
tabase that determines each radio's
affiliation(s) in Type II systems.
Another difference between the sys-
tems is that Type I systems are ar-
ranged in a fleet-subfleet hierarchy.
For example, it is possible for a city
using a Type I system to designate
four fleets, each with eight subfleets.
20-432.fm Page 30 Friday, July 14, 2000 11:30 AM