System Description - Ericsson MDX GE-MARC Maintenance Manual

LBI-38960
Table 1 - Tone & Digital Channel Guard
TONE CG DIGITAL CG
No CG 023
67.0 025
71.9 026
74.4 031
77.0 032
79.7 043
82.5 047
85.4 051
88.5 054
91.5 065
94.8 071
97.4 072
100.0 073
103.5 074
107.2 114
110.9 115
114.8 116
118.8 125
123.0 131
127.3 132
131.8
134
136.5 143
141.3 152
146.2 155
151.4 156
156.7 162
162.2 165
167.9
172
173.8 174
179.9 205
186.2 223
192.8 226
203.5 243
210.7 244
245
251
* Codes Unique to Ericsson/GE
To reverse the polarity of the digital Channel Guard codes, type I (for "Inverted") before the code number, i.e. I023
4
DIGITAL CG DIGITAL CG
261 654
263 662
265 664
271
703
306 712
311 723
315 731
331 732
343 734
346 743
351
754
364 036*
365 053*
371 122*
411 145*
412
413 212*
423
225*
431 246*
432 252*
445 255*
464 266*
465 274*
466 325*
503 332*
506 356*
516 446*
532 452*
546 454*
565 455*
606 462*
612 523*
624 526*
627
631
632
NOTE

SYSTEM DESCRIPTION

The MDX GE-MARC trunked mobile radio system pro-
vides fast access to available RF channels and a degree of pri-
vacy due to selective signaling. This also eliminates
annoyance of other system user's conversations while ensuring
that intended calls are not missed. The trunked mobile radio
system consists of a repeater for each channel and the user's
mobile radio units. Tone signaling is used, with each mobile
being assigned two and/or four tone, tone sequences for group
designation. All mobiles in a group are assigned the same
tones, so that any unit can talk to all other units in the same
group.
When originating a call, the mobile identifies an idle re-
peater channel and interrogates it with a single burst of "busy"
tone. The repeater keys its transmitter and sends a burst of "ac-
quisition" tone back to the mobile unit. When the interrogating
mobile detects the acquisition tone, it transmits its collect and
group tones. These are regenerated by the repeater and "heard"
by all idle mobile units in the system.
All system idle mobiles continually scan all channels to de-
tect collect tones. Having now "heard" the collect tones they
hold on the channel and wait for the group tone(s) to follow.
If the listening mobiles detect the "correct" tone sequence
(the sequence of its own group), they lock on the channel, alert
their operators of an incoming call and open their audio cir-
cuits. If the "correct" group tones are not detected, the mobiles
remain in the idle state and continue to scan all channels for a
collect tone. Once a mobile is "locked" on a channel, it re-
mains there until the repeater times out or the operator termi-
nates the call.
OPERATIONAL MODES
The mobile radio is always in one of three operational
modes; idle, wait, or ready. The three operational modes and
the conditions that cause the radio to switch from one mode to
another are shown in Figure 1 (next page).
The radio enters idle mode as soon as it is turned on and
begins scanning channels for incoming calls. The wait mode is
entered when the user places a call. The radio remains in the
wait mode if no channel is available, or until a channel is ac-
quired. The ready or conversation mode is indicated by an
alert tone and the mode indicator on the control panel.
A tone signalling Timing Diagram is shown in Figure 2.
Sequence Flow Charts for each operational mode are
shown in Figures 3, 4, and 5.
LBI-38960
Figure 1 - Operational Modes
IDLE MODE (Figure 3)
When a mobile radio is in the Idle mode, the audio is
muted and all channels programmed for call decode are se-
quentially scanned for an incoming call. An incoming call is
identified when the mobile detects one of the collect tones pro-
grammed for the area. Upon receipt of a collect tone, the mo-
bile waits on the channel for a short interval to receive the
group or individual tone sequence sent by the calling mobile.
If a group or individual tone sequence is identified as belong-
ing to the listening mobile, the mobile then looks for busy tone
for 90 milliseconds. If four tones are properly decoded, the
mobile then looks for busy tone for 270 milliseconds.
If tone sequences received do not pertain to the listening
mobile, the mobile remains in Idle mode and resumes scanning
the channels looking for another collect tone. If the expected
sequences are detected the mobile enters the Ready mode.
While in Idle mode, removing the handset from the hanger,
pressing the PTT switch, or pressing the send key on the hand-
set, causes the radio to enter the Wait mode.
WAIT MODE (Figure 4)
When the user enters Wait mode, the group tone is checked
to make sure it is a valid call-originate group. If it is not valid,
a high frequency steady tone is heard. If valid, the radio scans
the call originate frequencies for brief intervals until it finds