Radio Shack PRO-2051 - Manual (Page 63)

63
Beyond the Basics
tracking Motorola systems
There are really two types of Motorola trunking systems.
These are usually referred to as Type I and Type II systems.
Type I only occurs on some 800 MHz systems. All VHF and
UHF trunking systems use Type II. One important distinction
between these two systems is the amount of data transmitted
by each radio when its push-to-talk button (PTT) is pressed.
Every radio in a trunked system is assigned a unique ID so
the central site computer can identify it when it’s used. Both
Type I and Type II systems place radios (or radio users) into
groups, called talk groups, and these talk groups are also
assigned unique IDs. Some radios have access to only one
talk group, while others have access to many talk groups.
The talk group(s) each radio can access is called the radio’s
affi liation(s). In a Type II system, when someone uses their
radio, only the radio ID is transmitted when PTT is pressed,
whereas in a Type I system the radio ID and its current
affi liation are both transmitted when PTT is pressed.
Why the difference? Type II systems are slightly more
advanced because the central computer maintains
a database which is used to determine each radio’s
affi liation(s).
Changes to a Type II system are easier than Type I because
the system manager only needs to update the database
instead of reprogramming individual radios.
Another difference between the systems is that Type I
systems are arranged in a fl eet-subfl eet hierarchy. For
example, it is possible for a city using a Type I system to
designate 4 fl eets, each with 8 subfl eets. Their fl eets might
be the police department, the fi re department, utilities, and
administration. The police may decide to further divide their
fl eet into subfl eets such as dispatch, tactical operations,
detectives, north, south, east and west side patrols, and
supervisors. All the available police radios would then be
assigned to one of the police subfl eets. Determining the