Ericsson DUAL FORMAT MDX LBI-38848A User manual

Maintenance Manual
LBI-38848A
Printed in U.S.A
Mobile Communications
DUAL FORMAT MDX
806 - 870 MHz MOBILE
TABLE OF CONTENTS
RF BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . LBI-38849
SYSTEM BOARD . . . . . . . . . . . . . . . . . . . . . . . LBI-38842
AUDIO/LOGIC BOARD . . . . . . . . . . . . . . . . . . . LBI-38843
AUDIO AMPLIFIER BOARD . . . . . . . . . . . . . . . . LBI-38844
FRONT CAP ASSEMBLY . . . . . . . . . . . . . . . . . . LBI-38850
PA BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . LBI-38302
SERVICE SECTION . . . . . . . . . . . . . . . . . . . . . LBI-38851

TABLE OF CONTENTS
Page
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
RF BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Synthesizer Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Transmit Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Receiver Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
POWER AMPLIFIER BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
AUDIO/LOGIC BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
SYSTEM BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
FRONT CAP ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
ACCESSORIES AND OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
PC PROGRAMMER OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
PC PROGRAMMED OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Carrier Control Timer (CCT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Channel Guard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Squelch Tail Elimination (STE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Retry Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
HARDWARE AND HARDWARE OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
OPTION CABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
NOISE SUPPRESSION KIT OPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
POWER CABLE OPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
EXTERNAL SPEAKER OPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
EXTERNAL ALARM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
EDACS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
CONVENTIONAL MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
GE-MARC V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Operational Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Idle Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Ready Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
GLOSSARY OF GE-MARC V SYSTEM TERMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
RADIO OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
USER INTERFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
ALERT TONES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
EDACS APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
GE-MARC APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
ASSEMBLY DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
INTERCONNECT DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
SPECIFICATIONS*
GENERAL
Operating Voltage 13.8 Volts ±20%
Battery Drain
Receiver (13.8 Vdc)
Off 0.01 Amperes (maximum)
Squelched 0.65 Amperes (maximum)
Unsquelched 2.0 Amperes (maximum at 10 Watts audio,
External Speaker)
Transmitter (13.8 Vdc) 10.5 Amperes (maximum at 25 Watts RF)
Channel Spacing 25 kHz (12.5 kHz NPSPAC)
Frequency Stability ±1.5 PPM (±0.00015%)
Temperature Range -30C to +60C (-22F to +140F)
Dimensions (H x W x D)
(Less Accessories)
Height 5.3 cm (2.1 inches)
Width 18.2 cm (7.2 inches)
Depth 24.0 cm (9.5 inches)
Weight 3.0 kg (6.6 pounds)
Antenna Impedance 50 Ohms
TRANSMITTER
Frequency Range 806.0125-824.9875 MHz
Output Power 25 Watts (Intermittent duty cycle; EIA 20%)
Audio Sensitivity 125 mVrms (typical)
Spurious and Harmonics <-16 dBm
Audio Distortion 5% maximum
Modulation Limiting +5 kHz maximum (4 kHz max 821.000 - 824.9875 and
866.000 - 869.9875 MHz)
FM Hum and Noise -45 dB
Audio Frequency Response Within +1, -3 dB of a 6 dB/octave pre-emphasis curve
Per EIA Standards from 300-3000 Hz
RECEIVER
Frequency Range 851.0125-869.9875 MHz
Acceptable Frequency Displacement ±2.5 kHz minimum
Sensitivity (12 dB SINAD) -113 dBm minimum
Spurious Response 70 dB minimum
Adjacent Channel Selectivity 68 dB minimum at ±25.0 kHz
Intermodulation Distortion 65 dB minimum
Audio Frequency Response Within +2, -8dB of a 6 dB/octave de-emphasis curve
from 300 -2700 Hz
Audio Output 10 Watts (External Speaker); 4 Watts (Internal Speaker)
Audio Distortion 5% maximum at 1 kHz
*These specifications are intended primarilyfor useby service personnel. Refer to the appropriate Specification Sheet
for complete specifications.
LBI-38848 LBI-38848
1

GENERAL DESCRIPTION
The Ericsson GE Dual Format MDX Mobile Radio is
a synthesized, wideband radio that uses integrated circuits
and microcomputer technology to provide high performance
trunked operation. This radio operates in the Enhanced Digi-
tal Access Communications System (EDACS), GE-MARC
trunking environments and in conventional communications
systems. The radio provides 25 Watts of RF power output in
the 806.0125-824.9875 MHz and 851.0125-869.9875 MHz
bands. The receiver operates in the 851.0125-869.9875MHz
band.
All radio functions are stored in a programmable Elec-
trically Erasable PROM (EEPROM). The radio is field
programmable using an IBM compatible personal computer
with the following equipment:
•Serial Programming Interface Module TQ3370
•Programming Cable (19B801417P10) TQ3372
•MDX Series Programming
Software (EDACS) TQ3373
•MDX Series Programming
Software (GE-MARC only) TQ3346
With the interface equipment and software, the com-
puter can be used to program (or re-program) customer
system frequencies, Channel Guard tones and options. Se-
lection of options is done during radio initialization using
the PC programmer.
The Dual Format MDXMobile Radio assembly con-
tains the following circuit boards and assemblies:
•Power Amplifier Board 19C851822G1
•RF Board 19D902123G22
•System Board 19D901891G2
•Audio/Logic Board 19D903963G1
•Audio Amplifier Board 19D904025G2
•Front Cap Assembly 19D904151G1
The circuit boards are all mounted on a main casting to
provide easy access for servicing. Interconnect plugs are
used to connect the boards to eliminate pinched wires and
other wiring problems.
RF BOARD
The RF Board includes the programmable frequency
synthesizer, transmitter exciter, receiver front end and IF
circuitry.
Synthesizer
The synthesizer circuit generates all transmit and re-
ceive RF frequencies. The synthesizer frequency is control-
ledbythemicroprocessorlocatedontheAudio/LogicBoard.
Frequency stability is maintained by a temperature compen-
sated reference oscillator module. Transmit audio is proc-
essed on the Audio/Logic Board and applied to the
synthesizer to modulate the VCO and TCXO. The buffered
VCO output drives both the transmitter exciter and the
receiver mixer.
Transmitter
The transmitter consists of a fixed-tuned exciter mod-
ule, a PAmodule and apower control circuit. The PAmodule
provides RF output to drive the antenna. The power control
circuit controls the PAmodule to maintain a constant output
power across the band. The RF output level is internally
adjustable for rated power. Thermistors inthe controlcircuit
protect the PA from overheating by reducing the power
output level.
Receiver
The dual conversion receiver circuit consists of a front
end section,45.3 MHz first IF, a 455 kHz second IF, and FM
detector. All audio processing and squelch functions are
accomplished on the Audio Board.
POWER AMPLIFIER BOARD
The PA board (19C851822G1) amplifies the RF board
output then connects it back to the RF board where it is
coupled through a PIN diode antenna switch, the low-pass
filter and the directional coupler to provide 25 watts power
output at the antenna connector.
AUDIO/LOGIC BOARD
The Audio/Logic Board provides all audio and digital
processing of the receive and transmit audio for digital
processing by the Logic Board. The board also contains
audio filtering, conventional analog tone processing, and the
receiversquelch.TheAudio/LogicBoardcontrolstheopera-
tion of the radio and digitally processes the receive and
transmit audio. The board contains a microprocessor and
associated memory circuits including an EPROM for con-
trolling the processor and a programmable "personality"
memory (an Electrically Erasable PROM - EEPROM) to
store customer frequencies, tones and options. The micro-
processor provides control data to the Audio Signal Proces-
sor (ASP), conventional tone generation and detection,
frequency data for the synthesizer, and sends and receives data
to another microprocessor on the Display Board for the LCD.
SYSTEM BOARD
The system board controls the main input power to the
radio. IGNITION SENSE input lead provides the necessary
signals to the MOSFET switching circuit. The board also
interfaces all option connectionsfrom theinternal boards inthe
radio with the optional items outside of the radio. All external
options for the radio,interconnect to the SystemBoard through
the back of the radio using an optional cable.
FRONT CAP ASSEMBLY
The Front Cap Assembly contains the Audio Amplifier
Board. The Audio Amplifier Board provides compression of
the microphone audio. It also provides audio compression for
the received audio in the discriminator and internal/external
speaker audio paths. A10-watt power amplifier is provided on
the board to drive a 4-ohm internal/external speaker.
ACCESSORIES AND OPTIONS
PC PROGRAMMER OPTIONS
The radio is programmed using an IBM compatible per-
sonal computer equipped with a RS-232 port. Option TQ3370
provides the RS-232 serial interface unit and the cable between
the PC and the unit. An auxiliary power supply for the unit is
also included but is not needed to program the radio.
Option TQ3372 provides the radio programming cable
between the PC interface unit and the radio microphone jack.
MDX PC programming software Option TQ3346 (GE-MARC
only) or TQ3373 (EDACS) is provided in both 3.5 and 5.25
inch diskettes.
PC PROGRAMMED OPTIONS
Carrier Control Timer (CCT)
The Carrier Control Timer turns off the transmitter after
the microphone push-to-talk (PTT) switch has been keyed for
a pre-programmed time period. A pulsing alert tone warns the
operator to unkey and then rekey the PTT to continue the
transmission. The timer can be programmed, using the PC
programmer. Any time periods between 30 seconds and 7.5
minutes can be programmed in 30 second increments. The
timer can be enabled or disabled for each channel.
Channel Guard
Channel Guard provides a means of restricting calls to
specific radios through the use of a Continuous Tone Coded
Squelch System (CTCSS), or a Continuous Digital Coded
Squelch System (CDCSS). Tone frequencies range from 67.0
Hz to 210.7 Hz in 0.1 Hz steps. There are 83 standard PC
programmable digital codes. The Channel Guard tone frequen-
cies and codes are software programmable. Both tone frequen-
cies and digital codes may be used. These codes and
frequencies are listed in Table 1 - Channel Guard Tone
Frequencies and Table 2 - Digital Channel Guard Codes
(see below).
Table 1 - Standard Tone Frequencies (Hz)
67.071.974.477.079.782.585.488.591.594.897.4
100.0 103.5 107.2 110.9 114.8 118.8 123.0 127.3 131.8 136.5 141.3
146.2 151.4 156.7 162.2 167.9 173.8 179.9 186.2 192.8 203.5 210.7
To reverse the polarity of the digital Channel Guard
codes in the PC programmer, type I ("inverted") before
the code number, i.e. I023.
NOTE
LBI-38848 LBI-38848
2

Squelch Tail Elimination (STE)
STE is used with tone and digital Channel Guard to
eliminate squelch tails. The STE burst is transmitted when
themicrophonePTTisreleased.Thereceivingradiodecodes
the burst and mutes the receiver audio for 250ms. This mute
time allows the transmission to end and to mute the squelch
tail. Theradio looks for STEon the received signalwhenthe
microphone is either on or off-hook. The STE is enabled for
transmit and/or receive by PC programming the radio’s
personality.
Retry Option
If no channel is free, the radio can be programmed to
activate the Call Retry state and display ’RETRYING’in the
display. Retrying causes the radio to revert to Idle mode and
scan for an incoming call while trying to acquire a free
repeater approximately every 5 seconds for a 2 minute pe-
riod.
HARDWARE AND
HARDWARE OPTIONS
The location and placement of systemhardware options
are shown on Sheet 4 of the 800 MHz Dual Format MDX
Mobile Interconnect Diagrams.
OPTION CABLE
Option Cable Option PMCD7Z (19C851585P14) is
used to bring all option connections from the System Board
through the back of the radio to the outside. This cable is
required with all external options.
NOISE SUPPRESSION KIT OPTION
Noise Suppression Kit Option PMPD1A (consisting of
Filter 19A148539G1 and Installation Manual LBI-31363) is
available for installations where excessive alternator or elec-
trical noises, present on the power cable, do not permit the
radio to operate properly. Refer to the interconnect diagram
for the radio and options.
POWER CABLE OPTION
18-foot Power Cable Option PMCD9A,
(19B801358P17), is available for installations requiring
more than the standard 9-foot cable.
EXTERNAL SPEAKER OPTION
External Speaker and Cable Option PMZM1T provides
the user with a five-inch waterproof speaker in a LEXAN
housing. PMCC9M is an 18 inch interconnecting cable for
the speaker. The radio’s 10-watt amplifier drives the
speaker’s 4-ohm impedance. The speaker leads are con-
nected to pins 2 and 9 of Option Cable Option PMCD7Z
(19C851585P14), using External Speaker Cable Option
PMCC9M (19A149590P8) (18 inches) included in the
PMZM5T kit. A 16-foot cable, Option PMCD1W
(19A149590P10) is also available.
EXTERNAL ALARM
External Alarm Horn Relay Option PMSU1C
(19A705499P1) can sound the vehicle horn when a call is
received. The option connects to pin 13 of Option Cable
Option PMCD7Z (19C851585P14) and is controlled by a
front panel option switch.
SYSTEM DESCRIPTION
EDACS
The Dual Format MDX mobile radio operates in either
EDACS (digital) mode, or in GE-MARC (tone) mode, pro-
viding customers another dimension of flexibility in opera-
tion. Both modes provide opportunities to increase RF
channel utilization through faster channel access and the
privacy inherent with selective signalling.
The EDACS system uses 9600 baud, high speed, digital
signalling to identify individual units, user groups, fleets,
and agencies. Agencies contain multiple fleets and fleets
contain multiple user groups (sub-fleets). By using this
addressing scheme, large user groups can be accessed simul-
taneouslyalltheway downtoindividualusers.Theprogram-
ming to determine transmit encoded groups and decoded
received groups is contained in the personality EEPROM of
the mobile. This information is individually programmed to
suit each users needs via the PC programmer for the radio.
The typical system configuration consists of at least 2
repeater stations (with a maximum number of 25) and the
associated mobiles. One repeater always is acontrol channel
dedicated to sending out continuous control data and also to
receive channel request data from the mobiles. When a
mobile isfirst turned on, it scans theavailable list of frequen-
cies programmed in the personality EEPROM for a control
channel. When a control channel is found, the mobile locks
on to the frequency and monitors the data for a channel
assignment (incoming call).
Table 2 - Digital Channel Guard Codes
PRIM.
CODE EQUIV. CODE PRIM.
CODE EQUIV. CODE PRIM.
CODE EQUIV. CODE PRIM.
CODE EQUIV. CODE
023 340,766 025 026 566 031 374,643
032 036 137 037 560,627 043 355
047 375,707 051 520,771 053 054 405,675
056 465,656 057 172 060 116,737 065 301
066 734 067 516,720 071 603,717,746 072 470,701
073 640 074 360,721 075 501,624 076 203,754
104 226,557 107 365 114 327,615 115 534,674
117 411,756 122 535 123 632,657 125 173
127 412,441,711 130 364,641 131 572,702 132 605,634,714
133 413,620 134 273 135 205,610 136 502,712
142 174,270 143 333 144 466,666 145 525
147 303,306,761 150 256,703 152 366,415 153 606,630
155 233,660 156 517,741 157 322,503 161 345,532
162 416,553 163 460,607,654 164 207,732 165 354
171 265,426 212 253 213 263,736 217 371,453,530
222 445,457,575 223 350,475,750 224 313,506,574 225 536
227 261,567 231 504,631,636 234 423,563,621,713 235 611,671,723
236 251,704,742 237 464,642,772 243 267,342 245 370,554
246 542,653 252 661 254 314,612,706 255 425
262 316,431,730 266 655 271 427,510,762 274 652
276 326,432 307 362,565 311 330,456,561 312 515,663,743
315 321,673 317 546,614,751 324 343,570 325 550,626
331 372,507 332 443,552 344 471,664,715 346 616,635,724
351 353,435 356 521 363 436,443,444,662 446 467,511,672
447 473,474,731,744 452 524,765 454 513,545,564 455 533,551
462 472,623,725 523 647,726,444,662 526 562,645
LBI-38848 LBI-38848
3

When receiving a channel assignment (incoming call),
the monitoring mobile immediately switches over to the
assigned voice channel and waits for a high speed data
confirmation message. Upon receipt of this message, the
voice paths are unmuted and the user can hear the call.
While on the voice channel, the mobile also continu-
ously monitors the low speed, 150 baud (subaudible) data
and carrier noise squelch to ensure consistent operation.
Upon loss of subaudible data reception (i.e., deep fade, or
out-of-range), the mobile returns to the control channel
frequency.
To initiate a call, theuser keysthe radio (which is locked
to the control channel), and a 30 millisecond high speed data
slotted channel request is transmitted to the control channel
receiver. The control channel processes the request from the
mobile and transmits back a voice channel assignment on an
unused channel.
When all available voice channels are in use, the control
channel places the mobile into a queue, transmits a queue
message back to the mobile, and will give a channel assign-
ment to the requesting mobile as soon as a voice channel is
free. If the system is busy and the station queue is filled to
capacity, a system busy message is returned totherequesting
mobile and an alert signal is given to the user.
After the initiating mobile receives a channel assign-
ment from the control station, it immediately switches fre-
quency over to the assigned voice channel and sends a burst
of 9600 baud dotting. The microphone voice paths are then
unmuted and the transmission begins. The transmitting mo-
bile also continuously sends out a subaudible tone (along
with voice) for system reliability. If the station loses this
signalling, the voice channel is muted and all receiving
mobiles are sent back to the control channel.
In normal operation, the transmitting mobile sends a
high speed data burst to indicate that the user has unkeyed,
causing all listening mobiles to switch back to the control
channel.
CONVENTIONAL MODE
In conventional mode (not trunked) the radio can oper-
ate either with tone Channel Guard, digital Channel Guard,
or carrier squelch, depending on personality programming.
Tone Channel Guard range is 67.0 to 210.7 Hz. Squelch Tail
Elimination (STE) is used with Channel Guard to eliminate
squelch tails at the receiving radio by phase shifting the
transmitted Channel Guard tone when the PTT is released.
Direct mode works identically to conventional mode
except that the transmit frequency band is changed to 851 to
870 MHz to permit direct mobile-to-mobile communica-
tions.
GE-MARC
The GE-MARC trunked mobile radio system consists
of a repeater for each channel and the users’ mobile radio
units. The system uses tone signalling with each mobile
being assigned two and/or four tone group tone sequences.
Groups of mobiles are assigned the same tones so that any
unit can talk to all other units in the same group. A block
diagram of the GE-MARC MDX is shown in Figure 1.
When originating a call, the mobile identifies an idle
repeater channel and interrogates it with a single burst of
"busy" tone; the repeater keys its transmitter and sends a
burst of "acquisition" tone back to the mobile unit. When
the interrogating mobile detects the acquisition tone, it then
transmits its collect and group tones which the repeater
regenerates for all idle mobile units in the system.
The idle mobiles, which continually scan all channels,
will stop on the active channel if any of the programmed
collect tones are detected and wait for group tone(s).
If the correct tone sequence is detected, the mobiles will
alert the operator of an incoming call and open their audio
circuits. If the correct sequence is not detected, the idle
mobiles will resume scanning the channels. Once the mobile
is "locked" on a channel, it will remain there until the
repeater times out or the operator terminates the call.
Operational Modes
The radio will always be 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 2.
The radio enters the Idle mode when power 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 until a channel is acquired, or if
no channel is available. The Ready or Conversation mode is
indicated by an alert tone and the mode indicator on the
control panel. Asignal timing diagram is shown in Figure 3.
Idle Mode
When the radio is in the Idle mode, the audio is muted
and all channels programmed for call decode are sequen-
tially scanned for an incoming call. An incoming call is
identified by detecting one of the collect tones programmed
in the area. Upon receipt of a collect tone, the mobile looks
for a short interval for the group or individual tones provid-
ing that their collect tones are the same. When no valid tone
is found, the mobile will resume scanning the channels for
an incoming call.
If a group (or individual decode) tone is detected, the
mobile then looks for busy tone for a 90 millisecond period. If
four tones are properly decoded, the mobile will then look for
busy tone for 270 milliseconds.
When no valid tones are found, the mobile will resume
scanning for a call with the next channel. When a busy tone is
found, the mobile will enter the Ready mode. If busy tone is
not detected,themobileremainsintheIdlemodeandcontinues
scanning channels looking for an incoming call.
Removing the handset from the hanger, pressing the PTT
switch or pressing the SEND key on the handset will cause the
radio to enter the Wait mode.
Wait Mode
When the user enters theWait mode, the display group is
checked to make sure it is a valid call-originate group. If it is
not valid, a low-frequency tone is heard for one second. If
valid, the radiowillscan the call-originatefrequencies for brief
intervals until it finds one withno busy tone on it. If no channel
is free, the radio, if programmed for this option, will activate
the Call Retry state and display "RETRYING" in the display.
Retryingwill causethe radio to revert tothe Idle modeandscan
for an incoming call while trying to acquire a free repeater
approximately every 5 seconds for a 2 minute period. If the
Retry option is not enabled, the mobile will sound the low-fre-
quency tone and then return to the Idle mode and display
"BUSY".
Figure 1 - GE-MARC Block Diagram
Figure 2 - GE-MARC Operational Modes
LBI-38848 LBI-38848
4

If a channel with no busy tone is found, the mobile trans-
mits a burst of busy tone to acquire the repeater. The repeater
then responds with a burst of acquisition tone. Upon receipt of
the acquisition tone, the mobile proceeds to transmit the group
tones (either two or four tones). If a four-tone sequence is sent,
the mobile must detect all four tones and busy tone before
entering the Ready mode. If a two-tone sequence is sent, the
busy tone must be present within 90 milliseconds of the last
tone in order for the radio to enter the Ready mode. If no busy
tone is present or if the four-tone sequence isn’t valid, the
mobile will jump to the next channel in the call originate set
and check for busy tone as described above.
Ready Mode
When an incoming call has been detected or an idle chan-
nel has been acquired, the mobile enters the Ready mode. In
this mode, the audio and push-to-talk circuits are enabled, the
speaker is unmuted, and the operator is alerted by an alert tone.
The radio can then be used in the conventional push-to-talk
manner with the radio remaining on the channel until the
operator hangs up or the repeater drops the busy tone causing
the unit to revert to Idle mode.
GLOSSARY OF GE-MARC TERMS
Idle Mode
In the "standby" condition, the mobile is inactive but
prepared to call or be called.The trunked radios areIDLE until
they are turned off.
Wait Mode
In the "attempting origination" condition, the Wait
mode is entered from Idle mode (only) as the user presses the
PTT switch on the microphone, or comes "off-hook". If
successful, the unit becomes READY. Otherwise, the unit is
IDLE or IDLE/WAIT after all channels are tried.
Ready Mode
In the "operating" condition, Ready is entered from
Idle mode viaWait mode when calling or directly from Idle
when called. Ready mode ends (the radio reverts to Idle)
when the user disconnects or with the loss of received Busy
Tone from the repeater. This normally occurs when the
repeater shuts down after communication is completed.
Busy Tone
A "Voice-plus" tone of 3051.9 Hz is the standard busy
tone. The 2918 Hz is the alternate busy tone. The busy tone
modulates mobile and repeater transmitters at a low level of
1 kHz deviation continuously.This tone is filtered out of the
received audio and is used to hold the communication chan-
nel active. It also excludes other mobiles from using the
channel when a call is active.
Acquisition Tone
A 1962.9 Hz tone sent at full deviation for 50 millisec-
onds from the repeater is used as acknowledgment from the
repeater that a busy tone was sent and signals the mobile that
signalling tones can now be sent.
Collect Tone
A tone chosen from 34 standardized frequencies, rang-
ing from 508.6 Hz to 2792.4 Hz, is used as the first tone in
the group tone sequence. The collect tone is used to gather
all mobiles with the same collect tone for decoding a call.
The duration of the tone varies as a function of the number
of channels which are programmed into the mobile and/or
repeater.
In a two-tone call, the mobile sends the collected tone
for a programmable duration. In the four-tone call, the mo-
bile always sends a 90-millisecond collect tone which the
repeater regenerates and sends for the correct duration.
Group/Individual Tones
Group/Individual Tones chosen from the 34 standard
frequencies follow the collect tone. In a two-tone call, the
second tone is sent for 450 milliseconds. In a four-tone call,
the second, third, and fourth tones are sent for 90 millisec-
onds from the mobile and 180 milliseconds from the re-
peater.
RADIO OPERATION
A complete set of operating instructions for the Dual
Format MDX are provided in LBI-38846 and are provided
with each radio.
This radio is flexible in operation and can be used in any
of three operating modes: Conventional radio system, En-
hanced Digital Access Communications (EDACS) system,
or GE-MARC (tone controlled) system. Either of the latter
two systems provide trunked channel selection for increased
channel utilization.
In an EDACS trunked environment, the user selects a
communications system and group. In this mode, audio
channel selection is transparent to the user and is controlled
via digital communication with the system controller. This
mode incorporatesadvanced programmablefeaturesandfast
access to communication channels.
In a GE-MARC trunked environment, the user selects a
communications areaand group. In thismode,audio channel
selection is also transparent to the user and is controlled via
tone signalling.
In Conventional mode, the user selects a channel and
communicates on that channel. In this mode, a system refers
to a set of channels and a channel is a transmit/receive radio
frequency pair.
The exact operation of any radio depends upon the
operating mode, the programming of the radio and the par-
ticular radio system. Most features described in these oper-
ating instructions can be enabled or disabled through
programming. Both of these important factors must be con-
sidered when addressing the following instructions.
USER INTERFACE
Operating controls are located on the radio front panel
and microphone.
The front panel LCD provides radio status and commu-
nication control information to the operator. The keypad is
used for manual number entry for individual calls access to
a telephone interconnect system and activation of various
EDACS, GE-MARC, and conventional features.
Turning The Radio ON/OFF
The radio is turned ON/OFF by pressing the PWR
button in the upper left corner of the front panel. A self
diagnostic test is performed when the radio is first turned on
if enabled through programming. To turn the radio OFF,
press the PWR button again.
If acall is initiated and a sequence of five beeps is sounded,
the user cannot access the radio system because the mobile
is out of receive range or is inoperative. Any subsequent
call will be ignored for 20 seconds.
NOTE
Figure 3 - Signal Timing
LBI-38848 LBI-38848
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ALERT TONES
TheDualFormatMDXradio generates aset ofunique
alerttonestoindicate operating status. The followingsection
identifies and describes the alert tones used in the Dual
Format MDXradio for Conventional, GE-MARC, and
EDACS applications.
EDACS APPLICATIONS
CALL
ORIGINATE
ALERT
If programmed, a short tone is sounded
whenever the Push-To-Talk key is
pressed and the radio has acquired a
channel. This tone indicates the user can
begin communications.
CALL QUEUED If one short, high-pitched tone sounds
after the transmitter is keyed, this indi-
cates that the system has placed the re-
quest in a queue. This tone sounds at
both the transmitting unit and the receiv-
ing unit(s) indicating to the user on the
receiving end that a call is being directed
to them. If the PTT is unkeyed while in
the queue, the radio autokeys (automat-
ically keys) Push-To-Talk when a chan-
nel becomes available (see AUTOKEY).
AUTOKEY When the PTT is keyed to place a call on
the system, but the PTT is released be-
fore getting to the channel (e.g. a queued
call), the radio automatically keys on the
channel when it gets the assignment. The
radio generates a long beepand holdsthe
transmitter keyed for two seconds.
Pressing the PTT button keeps the chan-
nel and sends the message before this
two second time-out has expired.
SYSTEM BUSY If you press the PTT key and hear three
short, medium-pitched tones, this indi-
cates that the receiving party is already
on the system or the system is busy and
its queue is full.You must rekey later to
access the system.
CALL DENIED Asingle, low-pitched beep sounds when
the PTT key is pressed and the request is
denied by the system.Thishappens if the
unit is an invalid user or if the unit is
requesting an unavailable service.
OUT-OF-
RANGE/
SYSTEM
INOPERATIVE
Asingle,low-pitchedtonesoundsimme-
diately after the PTTkey is pressed indi-
cating the radio is out of range of the
repeater. The radio tries to place the call
for a short period (3 seconds) after the
initialattempt.Theradiogeneratesasec-
ond low-pitched tone when it gives up
trying to place the call. These tones are
also heard if the system is off the air or
the radio needs servicing (evenwhenthe
radio is within calling range of the re-
peater).
GE-MARC APPLICATIONS
CALL
RECEIVED
ALERT
If programmed, a single alert tone
sounds when a group call is received and
a two-tone alert (one high followed by
one low tone) sounds for an individual
call.
CALL
ORIGINATE
ALERT
WAIT momentarily displays when a call
is being placed. Then a three-tone alert
is sounded to indicatethe callorigination
iscomplete.Thisindicates a channelwas
acquired and is ready for normal conver-
sation.
INVALID CALL
ORIGINATE
ALERT
Alow-frequency tone is sounded forone
second immediately after pressing PTT
and the display does not show WAIT.
This indicates a call was attempted
within a group that is not enabled for call
originate or an invalid dispatch overdial
call was attempted.
SYSTEM
TONES Alow-frequency tone is sounded for one second after attempting to place a
trunked call and BUSY is displayed.
This indicates that the GE-MARC sys-
temisbusy.Ifthe"CallRetry"optionhas
been enabled through programming, the
radio retries at 5 second intervals up to
15 times unless END is pressed, a chan-
nel is acquired, or an out-of-range con-
dition occurs.
OUT-OF-
RANGE
ALERT
If NO SVC is displayed and five beeps
are sounded after attempting to place a
trunked call, the radio is out of range of
the GE-MARC system. If the beeps
sound when the radio is within known
range of the system, the radio may need
servicing. If the "Call Retry" is active,
the radio tries the channel at twenty sec-
ond intervals for five minutes.
CARRIER
CONTROL
TIMER
(GE-MARC and Conventional operation.)
A pulsed-tone signal is sounded for a pre-
programmed time after PTT is pressed. Af-
ter nine seconds of pulsing the alert tone,
the radio unkeys the transmitter and com-
municationsareinterrupted.Whilethetone
is pulsing, the user can release and press
PTTagain to reset thetimer and resume the
conversation. In the conventional mode,
the radio unkeys and beeps until PTT is
released.
SYSTEM
TONES The GE MARC radio may generate other system tones to alert the user of custom
programmed events. Contact the GE-
MARC system operator for details about
these alert tones.
DUAL FORMAT MDXRADIO ASSEMBLY
ISSUE 1
PARTS LIST
SYMBOL PART NUMBER DESCRIPTION
APPLICATION ASSEMBLY
19D904183
— — — — ASSEMBLIES — — —
A1 19D902123G22 RF BOARD
A3 19D901891G2 SYSTEM BOARD
A4 19D904025G2 AUDIO AMPLIFIER BOARD
A5 19D903963G1 AUDIO/LOGIC BOARD
19C851822G1 PA BOARD
— — — — — — KITS — — — —
344A4253G1 Hardware Kit (No. 1)
344A4255G7 Hardware Kit (No. 2)
— — — — — CABLES — — — —
19A705301P6 Cable, Antenna
19B801467P1 Cable, J705 to J151
19B801467P2 Cable, J5 to J105
19B801454P36 Cable, RX to J104
19A705235P3 Cable, Ribbon, J901 on Audio Amplifier
to J902 on System Board
19B801454P38 Cable, Antenna to J7
19B801454P37 Cable, TX to J101
19B802397P1 Cable, Handset
— — — MISCELLANEOUS — —
19D904027P1 Casting
19C337683G2 Bracket
19D904185G1 Cover, Bottom
19D904186G1 Cover, Top
19D904187G1 Panel, Front
19B801358P18 Cable, 9 Foot, Power
19B235310P10 Nameplate, Combination
*COMPONENTS, ADDED, DELETED OR CHANGED BY PRODUCTION CHANGES
LBI-38848 LBI-38848
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ASSEMBLY DIAGRAM
(19D904183, Sh. 1, Rev. 1)
LBI-38848 LBI-38848
7

ASSEMBLY DIAGRAM
(19D904183, Sh. 2, Rev. 2)
LBI-38848 LBI-38848
8

ASSEMBLY DIAGRAM
(19D904133, Sh. 1, Rev. 2)
LBI-38848 LBI-38848
9

INTERCONNECTION DIAGRAM
(19D904133, Sh. 2, Rev. 2)
LBI-38848 LBI-38848
10

INTERCONNECTION DIAGRAM
(19D904133, Sh. 3, Rev. 2)
LBI-38848 LBI-38848
11