SmarTrunk ST-2112C User manual

ST-2112C (400Mhz ~ 470Mhz)
UHF FM DIGITAL TRANSCEIVER
SERVICE MANUAL
SmarTrunk Systems, INC.
ST-2112C SM R1.2

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
2
Table of Contents
1. Specifications: ...............................................................................................................................5
2. ST-2112 EXPLODED VIEW.............................................................................................................. 6
3. ST-2112 SIMPLIFIED DIAGRAM .....................................................................................................7
4. - ST-2112 RF DESCRIPTION................................................................................................................8
4.1. Circuit Configuration.................................................................................................................9
4.2. Receiver System........................................................................................................................ 9
4.2.1. Front-end RF Receiver...........................................................................................................9
4.2.2. ANALOG Audio Processing....................................................................................................9
4.2.3. Virtual Squelch Circuit...........................................................................................................9
4.2.4. Virtual VOLUME CONTROL..................................................................................................10
4.2.5. Sub audio signaling .............................................................................................................10
4.2.6. ANALOG AUDIBLE SIGNALING.............................................................................................10
4.2.7. DIGITAL AUDIO PROCESSING ..............................................................................................10
4.3. Transmitter System.................................................................................................................11
4.3.1. ANALOG TX SIGNAL.............................................................................................................11
4.3.2. DIGITAL TX AUDIO:..............................................................................................................11
4.3.3. Drive and Final Amplifier Stages .........................................................................................11
4.3.4. Automatic Transmit Power Control ....................................................................................12
5. RC-2112 ALIGNMENT..................................................................................................................13
5.1. Introduction ............................................................................................................................13
5.2. ALIGNMENT:............................................................................................................................13
5.3. Alignment Procedure ..............................................................................................................14
5.3.1. GENERAL ALIGNMENT CONSIDERATIONS:..........................................................................14
5.4. MAIN RADIO ALIGNMENT.......................................................................................................15
5.5. TRANSMITTER ALIGNMENT: ...................................................................................................15
5.5.1. Main Clock alignment: ........................................................................................................16
5.5.2. Transmit Power alignment:.................................................................................................17

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
3
5.5.2.1. High POWER LEVEL ALIGNMENT..................................................................................... 17
5.5.2.2. Mid POWER LEVEL ALIGNMENT......................................................................................18
5.5.2.3. LOW POWER LEVEL ALIGNMENT ....................................................................................18
5.5.3. ANALOG MAXIMUM DEVIATION ........................................................................................18
5.5.4. Modulation Gain alignment:...............................................................................................18
5.5.5. FDMA DATA MODULATION alignment: ..............................................................................19
5.5.6. TDMA DATA MODULATION alignment: ..............................................................................20
5.5.7. EIA tones Level Alignment: .................................................................................................20
5.5.8. DTMF signaling level alignment: .........................................................................................20
5.5.9. DCS signaling alignment:.....................................................................................................21
5.5.10. CTCSS signaling alignment ..................................................................................................21
5.5.11. FSK signaling alignment: .....................................................................................................22
5.6. RECEIVER ALIGNMENT ............................................................................................................23
5.6.1. DISCRIMINATOR GAIN.........................................................................................................23
6. COMPLEMENTARY RADIO ALIGNMENT......................................................................................24
6.1. BATTERY WARNING LEVEL ......................................................................................................24
7. COMPLIMENTARY USER ALIGNMENT.........................................................................................25
7.1. OPTION ALIGNMENT:..............................................................................................................25
7.1.1. ANALOG Microphone gain:.................................................................................................25
7.1.2. ANALOG External Mic Gain:................................................................................................25
7.1.3. ANALOG AGC......................................................................................................................26
7.1.4. DIGITAL AGC........................................................................................................................26
7.1.5. MINIMUM VOLUME LEVEL: ................................................................................................27
7.1.6. SQUELCH LEVEL:..................................................................................................................27
7.1.7. DISABLE RF POWER.............................................................................................................27
8. RADIO APPEARANCE ALIGNMENT ..............................................................................................28
8.1. DISPLAYS AND LEDS: ...............................................................................................................28
8.1.1. Auto backlight delay alignment: .........................................................................................28
8.1.2. Power on Text: ....................................................................................................................28

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
4
8.1.3. Leds: ....................................................................................................................................29
8.2. Tones.......................................................................................................................................29
8.3. ANNUNCIATION ......................................................................................................................29
9. ST-2112 SCHEMATIC ...................................................................................................................32
10. ST-2112 FROM BOARD SCHEMATIC............................................................................................33
11 ST-2112 COMPONENT LOCATOR (TOP LAYER) ...............................................................................34
12 ST-2112 COMPONENT LOCATOR (BOTTOM LAYER) .......................................................................35
13 ST-2112 PCB TOP LAYER..................................................................................................................36
14 ST-2112 PCB BOTTOM LAYER.......................................................................................................... 37
15 ST-2112 PCB GROUND LAYER .........................................................................................................38
16 ST-2112 PCB POWER LAYER............................................................................................................39
17 ST-2112 FRONT BOARD COMPONENT LOCATOR (TOP LAYER).......................................................40
18 ST-2112 FRONT BOARD COMPONENT LOCATOR (BOTTOM LAYER)...............................................41
19 ST-2112C BOM ................................................................................................................................42
20 ST-2112 KEYBOARD & DISPLAY BOM..............................................................................................52
21 ACCESSORY PORT:...........................................................................................................................53
22 ST-2112 SERVICE MANUAL REVISIONS ...........................................................................................55

1. Specifications:
SPECIFICATION
ST-2112C
GENERAL
Frequency Range [Mhz]
400 TO 470
Channels
512
Groups/Banks
64
Power [Vdc]
6.4 to 8.8
Dimensions [mm]
130(H)x36(D)x52(W)
Weight [gr] (oz)
320 - (11.3)
Temperature range
- 30 °C ~ 60 °C (-22°F ~ +140°F)
Signaling
51 CTCSS tones / 183 DCS tones / 65534 SDR IDs
Reverse Burst
No
Display
128x64 (supports international characters)
Emergency call
Yes
GPS
Option
Channel Scan
Yes
BCLO / BTLO
Yes
Power Saver control
Yes
TOT
Yes
Radio Kill/Alive
Yes
Adjustable Power Selection
Auto + H/M/L
Key lock
Yes
Adjustable Squelch Level
16 Step
Password
Yes
Key Function selection
Yes
TRANSMIT
MAX RF power
4 W
Frequency Stability
>1PPM
Bandwidth [Khz]
6.25/12.5/25
Adjacent Channel Power
-65dBC (typ)
SNR
45dB typ
Analog harmonic distortion
3% typ (AF 1Khz, 60% deviation)
Data transmit rate
2400/4800/9600 bps
Max frequency deviation
[email protected] BW/5Khz@25Khz BW
Analog Modulation type
11K0F3E, 25K0F3E
TDMA Emissions
8K30F7E, 8K30F7D
FDMA Digital emissions
6K25F1E, 6K25F1D, 8K30F1E, 8K30F1D, 8K30F1W
Ext. Mic. Impedance
600 Ohms
RECEIVER
Analog Sensitivity
0.25uV (12dB Sinad)
Digital Sensitivity
0.25uV (3% BER)
Image rejection
60dB typ
Adjacent Channel selectivity
65dB typ @25KHz BW
HUM and NOISE ratio
45dB
Speaker Audio Power
1W
External audio power
1W
Specifications subject to change without notice or obligation

2. ST-2112 EXPLODED VIEW
ST-2112V
Jack Chang
Daniel Martin
2 . ST-2112 EXPLODED VIEW

3. ST-2112 SIMPLIFIED DIAGRAM
LPF Ant Sw
D1/D3
Final
AMP
Q1
Power
Detection
D2
Driver
Q3
Buffer
AMP
Q2
TX CTRL
[U3]
CLOCK
[Y1]
POWER
CTRL
[U2]
FLASH
MEMORY
[U4]
RAM
MEMORY
[U7]
DISPLAY
GPS
G-SENSOR
PWM
KEYBOARD
SIDE
KEYS
USB
SERIAL
PORT
Main Processor
[U8]
Radio
U1
Audio Processor
Modem
[U5]
VOCODER
[U6]
CLOCK
[Y2]
MIC
AMP
[U12]
AUDIO
PA
[U10]
CLOCK
[Y3]
JP2

Notes:

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
9
4. - ST-2112 RF DESCRIPTION
4.1. Circuit Configuration
The receiver is a single receiver with
built-in DSP fully integrated.
Incoming signals from the antenna,
after passing through LPF filter, are
fed direct to the DSP down
converter to get the baseband voice
from 0Hz to 3500Hz.
Demodulated signals are filtered
and conditioned onto a second DSP
based filter, which also includes a
high efficiency 4FSK modem.
For digital demodulation, the
recovered data is fed into a vocoder,
which converts the data to voice.
Analog voice from the analog path
or the analog voice recovered from
the vocoder, are fed into an audio
power amplifier.
Transmit signal frequency is
generated by integrated VCO and
PLL. RF frequency generated by the
integrated RF chip is amplified into
a 3-step amplifier then filtered by a
low pass filter to be applied to the
antenna.
4.2. Receiver System
4.2.1. Front-end RF Receiver
Incoming RF signals from the
antenna are delivered to the
Receiver Unit and pass through a
Low-pass filter, antenna switching
diode, and then fed to the receiver
(U1) passing through a limiter BPF.
4.2.2. ANALOG Audio Processing
The RF signal is tuned by U1, which
includes a base band DSP audio
processing, recovering flat audio
from DC up to 3500 hz.
The detected audio is amplified,
filtered and conditioned inside of
U5 which also includes a de-
emphasize filtering shape for
received audio signals
The output of the filtered and
conditioned audio is delivered to an
audio power amplifier (U10) then to
the speaker passing through the
external audio connector switch.
4.2.3. Virtual Squelch Circuit
S/N ratio is measured by the
receiver (U1) as the result of the
analysis of the signal and the noise
of the carrier. The output is sent to
the main processor as a digital
frame, which is analyzed by radio
firmware, removing noise then
qualifying the signal level. If the
signal level is higher than the
LPF SWITCH
PROTECTION
FILTER
RECEIVER
[U1]
RECEIVER
[U1]
AUDIO
PROCESSOR
[U5]
AMPLIFIER
[U10]

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
10
expected for the current
programmed squelch threshold,
then the processor analyzes the
expected signaling programmed on
the current channel table.
In case of not any signaling is
required, or the signal has been
detected, the processor ask to the
audio processor (U5) to open the
audio path, unmuting the audio
amplifier (U10).
4.2.4. Virtual VOLUME CONTROL
The potentiometer position (RV1) is
measured by one analog to digital
converter on the audio processor
(U5), and then the information is
reported to the main processor. The
firmware immediately adjusts the
audio processor path gain to get the
appropriate overall circuitry volume
control.
Minimum volume, emergency and
private audio level are controlled
only by software overriding the
information received from the DAC
on U5.
4.2.5. Sub audio signaling
Received sub audio signaling like
CTCSS and DCS are received and
processed by the receiver (U1) then
detected on the audio processor
(U5). Once decoded, the sub audio
signaling is reported to the
processor where the firmware
compares it with the value
programmed into the current
channel programming.
If the received signaling matches
the channel programming, then the
main processor (U8) requests the
audio processor (U5) to open the
audio patch.
4.2.6. ANALOG AUDIBLE SIGNALING
DTMF signals, MDC1200 and tone
signals are processed and decoded
by the audio processor (U5).
Decoded information or received
tone is reported to the main
processor (U8).
4.2.7. DIGITAL AUDIO PROCESSING
Digital received information is
processed by the receiver DSP (U1)
then delivered to the audio
processor (U5), which includes a
high speed (4FSK) modem.
Data decoded by the modem is
transferred to the main processor
(U8) which de-encrypts the
information, checks the integrity,
corrects the wrong bits and extract
the audio information form the
received frame.
The portion of the data received,
error free, is moved to the vocoder
(U6).
The vocoder re-builds the audio
from the compressed data then
applies filter it, adjust the volume
RECEIVER
[U1]
AUDIO
PROCESSOR
[U5]
AMPLIFIER
[U10]
MAIN
PROCESSOR
[U8]
VOCODER
U6]

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
11
and fed it to the audio power
amplifier (U10).
4.3. Transmitter System
4.3.1. ANALOG TX SIGNAL
The AF signal from the internal
microphone (MK1) or external
microphone (J5) are processed as
differential signal, then it is
conditioned and transformed into
common mode by the microphone
pre-amplifier (U12).
The result of the conditioned in-
band filtered signal is fed to the
Audio Processor (U5), which
provides audio compander,
emphasize, limitation, encryption,
etc.
The high audio band of the signal
from 300 to 3500 Hz are directly fed
to the transmitter (U1), which
performs a direct modulation of a
generated carrier.
Low frequency signaling audio are
fed directly to Y1 VC TXCO main
clock generator and U1 with a
corresponding balance controlled
by software.
4.3.2. DIGITAL TX AUDIO:
The AF signal from the internal
microphone (MK1) or external
microphone (J5) are fed directly to
the vocoder chip (U6) which
perform the data codification,
delivering the digitized and encoded
audio as digital frames which are
processed by the Main Processor
U8, which add a FEC (Frame Error
Correction), encrypt the
information and add the user
related information as user ID, etc.
The final data frame is fed to the
Audio Processor (U5) which has a
built in modem, which operates for
FDMA or TDMA signals, controlling
the modulation of the Transmitter
(U1) through the VC TXCO for DC
to low frequencies and the direct
modulation for higher frequencies.
4.3.3. Drive and Final Amplifier Stages
Final RF is amplified on Q2
(2SC3356) then filtered to be fed to
Q3 (2SK3475) then finally amplified
by Q1 (2SK3476) up to 5 watts
output power.
The transmit signal then passes
through the antenna switch D1
(BAR63) and is low-pass filtered to
suppress harmonic spurious
radiation before delivery to the
antenna
AMPLIFIER
[U12]
AUDIO
PROCESSOR
[U5]
TRANSMITTER
[U1]
VC TXCO
[Y1]
AUDIO
PROCESSOR
[U5]
TRANSMITTER
[U1]
VC TXCO
[Y1]
MAIN
PROCESSOR
[U8]
VOCODER
[U6]

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
12
4.3.4. Automatic Transmit Power
Control
The RF power detector (RB705D)
detects transmitted feedback then
sends the readout to audio
processor U5 (CMX-7141). Audio
amplifier compares the transmitted
power against the referred level
stored on current channel memory
adjusting the power control level
generated as reference by one DAC
output on the same Audio
processor (U5) then amplified by U2
(MCP6241U) controlling the gate
current on Q1 and Q17.
Evenly when power level is adjusted
by software on three levels (Hi, Med,
Lo) the power value can be adjusted
to any desired value between zero
and 5Watts by the alignment
software.
Notes:

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
13
5. RC-2112 ALIGNMENT
5.1. Introduction
The ST-2112 series is carefully
aligned in factory for the specified
performance, across the frequency
range depending for each version.
Realignment should therefore not
be necessary except in the event of
a component failure, or altering
version type.
All component replacement and
service should be performed only by
an authorized SmarTrunk
representative, or the warranty
policy may be void.
The following procedures cover the
sometimes critical and tedious
adjustments that are not normally
required once the transceiver has
left the factory.
However, if damage occurs and
some parts subsequently are
placed, realignment may be
required. If a sudden problem
occurs during normal operation, it
is likely due to component failure;
realignment should not be done
until after the faulty component has
been replaced.
We recommend that servicing be
performed only by authorized
SmarTrunk service technicians
who are experienced with the
circuitry and fully equipped for
repair and align. Therefore, if a fault
is suspected, contact the dealer
from whom the transceiver was
purchased for instructions
regarding repair. Authorized
Smartrunk service technicians
realign all circuits and make
complete performance checks to
ensure compliance with factory
specifications after replacing any
faulty components.
Those who do undertake any of the
following alignments are cautioned
to proceed at their own risk.
Problems caused by unauthorized
attempts at realignment are not
covered by the warranty policy.
Also, SmarTrunk reserves the right
to change circuits and alignment
procedures in the interest of
improved performance, without
notifying owners.
Under no circumstances should
any alignment be attempted unless
the normal function and operation
of the transceiver are clearly
understood, the cause of the
malfunction has been clearly
pinpointed and any faulty
components replaced, and
realignment determined to be
absolutely necessary.
5.2. ALIGNMENT:
The following test equipment (and
thorough familiarity with its correct
use) is necessary for complete
realignment. Correction of
problems caused by misalignment
resulting from use of improper test
equipment is not covered under the
warranty policy.
While most steps do not require all
of the equipment listed, the
interactions of some adjustments
may require that more complex
adjustments be performed
afterwards. Do not attempt to
perform only a single step unless it
is clearly isolated electrically from

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
14
all other steps. Have all test
equipment ready before beginning,
and follow all of the steps in a
section in the order presented.
Required Test Equipment
RF Signal Generator with
calibrated output level at 1
GHz
Deviation Meter (linear
detector)
In-line Wattmeter with 5 %
accuracy at 1 GHz
50 Ohm RF Dummy Load
with power rating 10W at 1
GHz
8 Ohm AF Dummy Load
(Attention: Audio output is
BTL output)
Regulated DC Power Supply
(standard 7.5 V DC, 3 A)
Frequency Counter with 0.2
ppm accuracy at 1GHz
Audio Generator
AC Voltmeter
DC Voltmeter
UHF Sampling Coupler
IBM PC / compatible
Computer with Microsoft®
Windows® XP or later
operating system
SmarTrunk SDR
Programming software
(version 1.0.2 or later)
USB A/B Programming Cable
5.3. Alignment Procedure
Alignment Preparation &
Precautions
A 50-Ohm RF Dummy Load and in-
line wattmeter must be connected
to the main antenna jack in all
procedures that request for
transmission, except where
specified otherwise. Correct
alignment is not possible with an
antenna.
After completing one-step, read the
following steps to determine
whether the same test equipment
will be required. If not, remove the
test equipment (except dummy load
and wattmeter, if connected) before
proceeding.
Correct alignment requires that the
ambient temperature be the same
as that of the transceiver and test
equipment, and that this
temperature be held constant
between 68°F and 86 °F (20°C ~ 30
°C). When the transceiver is
brought into the shop from hot or
cold air, it should be required to
wait few minutes to come to room
temperature before alignment.
Whenever possible, alignments
should be made with oscillator
shields and circuit boards firmly
affixed in place. Also, the test
equipment must be thoroughly
warmed up before beginning.
Note: Signal levels in dB referred to
in the alignment procedure are
based on 0 dBm EMF = 1 mV.
5.3.1. GENERAL ALIGNMENT
CONSIDERATIONS:
Evenly if the radio is powered off,
the alignment software will detect
it, but some of the test cannot be
performed correctly.
Please be sure you turn the radio on
before continue with this alignment
procedure.

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
15
In case the battery has not enough
charge, the test will be aborted by
the software. Please ensure the
battery has more than 50% of
remaining charge to complete the
test.
5.4. MAIN RADIO ALIGNMENT
Before setup any parameter, run
SDR programming software then
select Radio Alignment from top bar
menu.
A complementary message will be
displayed on the time the software
detects the radio connected to USB
port on the computer.
If the radio isn’t connected, then the
program will be timed out after 20
seconds.
As soon as the radio is detected,
actual radio parameters are loaded.
Once the radio is connected, a new
screen pops up showing all
alignment parameters. The
software downloads actual
alignment parameters stored into
radio memory, so the information
displayed on each alignment step is
the real value form the previous
alignment.
The radio also stores in a special
memory area, original values
assigned in factory. You can go
back to those values anytime for
any particular alignment step.
In case the radio is password
protected, dealer password is
required to access to this alignment
menu.
At any time, press to end
the alignment procedure then the
radio will returns to alignment
menu.
For any transmit related alignment
parameter, low power will be used.
5.5. TRANSMITTER ALIGNMENT:

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
16
7.5V Power Supply
PC compatible
On Line Wattimeter
30dB pad
Deviation Meter
Frequency Counter
Setup the test equipment as shown
for transceiver alignment, apply 7.5
V DC power to the transceiver.
The RF parameters are typed on the
alignment software to facilitate the
alignment within all radio band
avoiding special programming of
the radio before start alignment
procedure.
All parameters can be aligned
without relationship to any other,
so there is no an order to align. On
this way, you can adjust only the
desired parameter, avoiding to
waste time realigning other
parameters than required.
Before proceed to align any
parameter, a desired frequency
must be loaded into both TX and
RX. Evenly when the radio has
stable characteristics for all
bandwidth, it is recommendable to
align on middle of the radio working
band.
5.5.1. Main Clock alignment:
To align the main clock for radio Tx
and RX, please select Main Clock
Alignment option Alignment screen.
Fig 12: alignment menu
Actual alignment value will be
displayed on alignment slider.
Press [Start] then move the slider to
reach the desired value at the time
you checks the Frequency Counter
to reach the desired frequency as
shown on Frequency field of the
alignment screen.
As soon the desired value is
reached, press [Finish] to store the
value on radio memory.
If you want to retrieve factory
default, press [Factory] instead of
[Start]. You will be asked to confirm
the factory default alignment, and
then if you confirm it, original
values from factory will be loaded
into current alignment settings.
This confirmation screen will
appears any time you want to
realign any parameter to Factory
Default.

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
17
5.5.2. Transmit Power alignment:
ST-2112 has three power levels to
be selected for each channel. High,
medium and low power level can be
aligned as per radio usage
requirement.
For power alignment, you can do a
fine tuning as per your desire
frequency sub-band. The software
lets you linearize the complete band
“cutting” the complete band into
five steps to let you focus into your
frequency bands.
Even when the software has already
assigned the most convenient
frequency points to consider the
alignment, you still can enter
exactly the frequency of your
interest.
5.5.2.1. High POWER LEVEL
ALIGNMENT
To align the High Power level select
Power High Level.
Software automatically retrieves
actual level to the alignment slider.
This level has been aligned in
factory, but you still can adjust it as
per your desires.
To realign, please select [Start] then
move the slider or introduce the
value manually at the time you
check the real transmit power on
the wattmeter connected to the
radio as recommended on TX
alignment diagram.
As soon as [Start] is pressed, the
radio start to transmit a carrier, so
please verify the antenna dummy
load is properly connected to avoid
any damage to the transmitter.
As soon the desired value is
reached, press [Finish] to store the
value into radio memory.
If you want to load default High
power only, keeping any other value
without any change, press [Factory]
instead of [Start]. A pop up window
will ask you to confirm the default
parameters upload to the radio
power.
Press [OK] to confirm.
As descripted previously, you can
manually select the frequency
range to align, divided into five
different sub-ranges.
You can also define the right
frequency of interest to align, typing
the desired one into the frequency
field:
If selected frequency is not
supported by radio hardware, the
frequency field will be filled on red.
In case the PLL is locked, then it
becomes filled on green.
Please be sure that the PLL is
locked as soon as you press [Start],

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
18
otherwise the alignment should be
not correct.
5.5.2.2. Mid POWER LEVEL
ALIGNMENT
Repeat the same procedure to align
High Power, but select Power
Medium Level on the alignment
menu.
5.5.2.3. LOW POWER LEVEL ALIGNMENT
Repeat the same procedure to align
High Power, but select Power Low
Level on the alignment menu.
5.5.3. ANALOG MAXIMUM DEVIATION
Maximum deviation for analog
signals modulated from ST-2112
can be aligned by Max Deviation
alignment option from the
alignment menu.
Actual alignment value will be
displayed on alignment slider.
Press [Start] then move the slider to
reach the desired value at the time
you checks the deviation meter to
reach the desired signaling level for
narrow band operation. Radio will
generate a 1000Hz alignment
reference tone for alignment
proposes.
As soon the desired value is
reached, press [Finish] to store the
value on radio memory.
Wide band channels uses the same
limiter. No additional wide band
max deviation alignment is
required.
If you want to retrieve factory
default, press [Factory] instead of
[Start]. You will be asked to confirm
the factory default alignment, and
then if you confirm it, original
values from factory will be loaded
into current alignment settings
5.5.4. Modulation Gain alignment:
This is a critical parameter which
may not be realigned to different
values other than factory default.

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
19
Lower gain means a very high
microphone gain must be assigned
to get the proper radio voice
deviation, and higher gain means a
risk because the max deviation
limit must be reached by any signal
which makes the limiter to
introduce distortion to avoid over
deviation.
Under your risk, if you still prefer to
realign the overall modulation gain,
you must select Modulator Gain on
Alignment screen.
Actual alignment value will be
displayed on alignment slider.
Press [Start] then move the slider to
reach the desired value at the time
you checks the deviation meter to
reach the desired signaling level for
narrow band operation.
For this alignment step, the radio
does not generate any signal. It only
stores the new value of the overall
modulation gain into the memory.
As soon the desired value is
reached, press [Finish] to store the
value on radio memory.
If you want to retrieve factory
default, press [Factory] instead of
[Start]. You will be asked to confirm
the factory default alignment, and
then if you confirm it, original
values from factory will be loaded
into current alignment settings.
5.5.5. FDMA DATA MODULATION
alignment:
To align 4FSK signaling deviation
for FDMA mode, select FDMA
Deviation on Alignment screen.
Actual alignment value will be
displayed on alignment slider.
Press [Start] then move the slider to
reach the desired value at the time
you checks the deviation meter to
reach the desired signaling level for
narrow band operation. Radio will
generate a 1000Hz reference tone
for alignment proposes.
As soon the desired value is
reached, press [Finish] to store the
value on radio memory.
If you want to retrieve factory
default, press [Factory] instead of
[Start]. You will be asked to confirm
the factory default alignment, and
then if you confirm it, original
values from factory will be loaded
into current alignment settings.

ST-2112C SM R 1.2 SMARTRUNK SYSTEMS, INC.
20
5.5.6. TDMA DATA MODULATION
alignment:
To align 4FSK signaling deviation
for TDMA mode, select TDMA
Deviation on Alignment screen.
Actual alignment value will be
displayed on alignment slider.
Press [Start] then move the slider to
reach the desired value at the time
you check the deviation meter to
reach the desired signaling level for
narrow band operation. Radio will
generate a 1000Hz reference tone
for alignment proposes.
As soon the desired value is
reached, press [Finish] to store the
value on radio memory.
If you want to retrieve factory
default, press [Factory] instead of
[Start]. You will be asked to confirm
the factory default alignment, and
then if you confirm it, original
values from factory will be loaded
into current alignment settings.
5.5.7. EIA tones Level Alignment:
EIA signaling generated by ST-2112
must be aligned by selecting EIA
Tones Level alignment option from
the alignment menu.
Actual alignment value will be
displayed on alignment slider.
Press [Start] then move the slider to
reach the desired value at the time
you check the deviation meter to
reach the desired signaling level for
narrow band operation. Radio will
generate a 1000Hz reference tone
for alignment proposes.
As soon the desired value is
reached, press [Finish] to store the
value on radio memory.
If you want to retrieve factory
default, press [Factory] instead of
[Start]. You will be asked to confirm
the factory default alignment, and
then if you confirm it, original
values from factory will be loaded
into current alignment settings.
5.5.8. DTMF signaling level alignment:
DTMF signaling generated by ST-
2112 must be aligned by selecting
DTMF Level alignment option from
the alignment menu.