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24
Understanding Scanning
If you are a new scanner enthusiast, you might want to
read the first part of this manual and use your scanner in
conventional mode before you begin trunk tracking.
Understanding scanning fundamentals and terminology
will make trunk tracking much easier. If you are already
an experienced scanner operator, you might want to go to
“Programming Motorola Systems” on Page 53, “Program-
ming EDACS Systems” on Page 57, or “Programming
LTR Systems” on Page 59 now.
Types of Trunking Systems
Trunking systems divide a few frequencies among many
different users, but the way that each system does this is
slightly different. This section describes some of the
technical data behind Motorola, EDACS, and LTR trunked
radio systems.
Motorola Trunking
While there are different types of Motorola trunking
systems, they all use the same basic trunking method.
The system consists of one control channel (or as many
as 4 per system), plus one or more voice channels
(typically 10, 20, or 28 total channels). When a user
presses Push To Talk (PTT) to transmit, their radio first
sends their talk group information to the control channel.
The computer then assigns that talk group to a specific
voice channel and transmits that data over the control
channel. All radios in that talk group switch over to the
assigned voice channel and the user can begin speaking.
This all typically takes place in about a second...the
person transmitting hears a beep from their radio when
the channel is assigned and then it is OK to start talking.
The systems in use are:
Motorola Type I – the radios send the radio ID, the fleet
and subfleet talk group ID to the control channel each
time they transmit. To program a Type I system, you need
to know the system’s fleet map. The most common fleet
maps are included in
“Preset Fleet Maps” on Page 103.
You can also find fleet map resources on the web.