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Service Manual
Analog Cellular
The simplified block diagram on page 1 - 7
illustrates an imaginary layout of one side
(Band A, or Band B) of a hypothetical service
area. The hexagons represent cells, and some
of the cell sites shown here also illustrate the
fact that an antenna tower and set of base
stations are associated with each site. In a
real world environment individual cells do
not have the hexagonal shape but may take
any form as dictated by the environment.
The cell sites are in communication with in-
dividual portable and mobile cellular tele-
phones. These portables and mobiles may
move from cell to cell, and as they do they
are " handed off" under the supervision of the
Figure 3. Channel Assignments
Cellular
Switch
Telephone
Company
Central Office
©2000 Motorola, Inc.
central controller (switch).
As illustrated(figure 3.) by the antenna tower
on the upper left, cell sites transmit overhead
messages more or less continuously even if
there are no mobiles or portables active
within that cell.
The switch (center left) is in control of the
system and interfaces with the central office
of the telephone company. As illustrated by
the deskset telephones, the telephone com-
pany interfaces with the entire landline net-
work.
The cell sites and the mobiles and portables
communicate through the use of data or, in
the case of AMPS, through the use of data
and tones. A complete analysis of data sig-
naling is beyond the scope of this manual.
Refer to the Electronic Industries Association
standard EIA-553 for a thorough discussion
of AMPS signaling protocol, or to Motorola' s
NAMPS Air Interface Specification for
NAMPS.
The tones used in AMPS signaling are Sig-
naling Tones and Supervisory Audio Tones.
NAMPS uses sub-audible digital equivalents.
Signaling Tone (ST) and Digital ST (DST)
In AMPS, signaling tone is a 10 kHz signal
used by the mobile or portable on the reverse
voice channel (REVC) to signal certain ac-
tivities or acknowledge various commands
from the cell site, including hand-offs, alert
orders, and call terminations, and to indicate
switch-hook operation. Various burst lengths
are used for different ST activities. On
NAMPS channels ST is replaced by a digital
equivalent called Digital ST (DST) which is
Cellular Overview
Analog Cellular
5
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