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Service Manual
The cellular telephone tunes to the assigned
voice channel and verifies the presence of the
proper forward SAT frequency (or DSAT mes-
sage). If SAT (DSAT) is correct the telephone
transponds SAT (DSAT) back to the cell site
and unmutes the forward audio. The cell site
detects reverse SAT (DSAT) from the cellu-
lar telephone and unmutes reverse audio. At
this point both forward and reverse audio
paths are unmuted and the cellular telephone
user can hear the other end ring, after which
conversation can take place. SAT (DSAT) is
sent and received more or less continuously
by both the base station and the cellular tele-
phone. However, SAT (DSAT) is not sent dur-
ing data transmissions, and the cellular tele-
phone does not transpond SAT continuously
during VOX operation. Also, DSAT is sus-
pended during the transmission of DST.
Notice that SAT and Signaling Tones are only
used on AMPS voice channels, and that the
Signaling Tone is only transmitted by the cel-
lular telephone.
Receiving a Call (Land to Mobile)
Once a cellular telephone has gone into ser-
vice, it periodically scans the overhead mes-
sage information in its memory and moni-
tors the paging messages for its telephone
number. When a page match occurs the
cellular telephone scans each of the access
channels and tunes to the strongest one. The
cellular telephone then acknowledges the
page on that access channel and thus noti-
fies the central controller of its cell location.
The switch then assigns a voice channel and
a SAT (DSAT) to the cellular telephone. The
cellular telephone tunes to the voice chan-
nel, verifies the presence of the proper SAT
frequency (DSAT message) and transponds
the signal back to the cell site. At the cell
site, the reception of SAT (DSAT) signals the
central controller that the cellular telephone
is ready for the call. An alert order is then
sent to the cellular telephone which responds
with a 10 KHz signaling tone (DST message).
The subscriber unit rings for 65 seconds or
until the user answers. Then the 10 KHz
signaling tone (DST message) is terminated
to alert the central controller that the user
has answered. The switch then connects the
incoming call to the appropriate circuit lead-
ing to the cell in contact with the cellular tele-
phone. At this point both forward and re-
verse audio paths are unmuted and the con-
versation can take place. SAT (DSAT) is sent
more or less continuously by the base sta-
tion and transponded by the cellular tele-
phone, except during data transmission.
DSAT is suspended during DST transmis-
sion, and during VOX operation SAT (DSAT)
is not transponded continuously by the cel-
lular telephone.
©2000 Motorola, Inc.
Cellular Overview
Analog Cellular
11
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