Digitrax DH126MT User manual

© 2016 Digitrax, Inc. www.digitrax.com— 1 —
Features:
▪FX3Function outputs for prototypical lighting eects and on/o control:
Constant Brightness Lighting with directional or independent control.
Realistic Eects like Ditch lights, Mars lights, strobes, and many more
FX3 & Standard Function Qualiers operate functions based on direc-
tion, F0 on or o, direction and F0, and whether loco is moving.
Function Remapping for custom function setup.
Master Light Switch turns o all lights & functions with one keystroke.
Advanced Consist Function Controls
▪Digitrax LocoMotion® System-Your locomotives look like the real thing.
The Digitrax LocoMotion System makes them run like the real thing, too!
Torque Compensation for smooth as silk silent operation.
128 Speed Step operation (14 or 28 steps can also be used).
Momentum with acceleration and deceleration.
Normal Direction of Travel is user selectable.
Switching Speed feature for easier and faster access to yard speeds.
3 Step Speed Tables set start, mid and max voltage for custom control.
28 Step Speed Tables with 256 level resolution for precise control.
▪Program CVs using any Digitrax Compatible Control system without having
to buy any extra equipment.
▪Compatible with Locomotives using the NMRA 21MTC Interface
▪Series 6 Decoder Features.
▪Works with PX112-2 Power Xtender.
▪Congurable FX3 Pulse Function available on all function outputs.
▪2 Digit and 4 Digit Addressing.
▪Basic, Advanced & UniVersal Consisting.
▪SuperSonic motor drive for silent operation.
▪Direct mode programming.
▪Decoder Reset CV with or without speed table reset.
▪Transponder Equipped ready for transponding on your Layout.
▪Motor Isolation Protection helps prevent damage to your decoder.
▪DCC Compatible.
▪FCC Part 15, Class B RFI compliant.
▪Digitrax “No Worries” Warranty.
DH126MT
Fits HO Scale
Locomotives
.805”x.64”x.17”
20.45mm x 16.26mm x 4.32mm
HO Scale
Mobile Decoder
21MTC interface
1.5 Amp/2 Amp Peak
2 FX3 Functions, 0.5 Amp
Complete Train Control
Run Your Trains, Not Your Track!

© 2016 Digitrax, Inc. www.digitrax.com— 2 —
Parts List
1 DH126MT Function Decoder
1 Instruction Sheet
Installation Information
See the Digitrax Decoder Manual for complete decoder test procedures, instal-
lation instructions, programming and technical information. Digitrax manuals
and instructions are updated periodically. Please visit www.digitrax.com for the
latest versions, technical updates and additional locomotive-specic installation
instructions. CAUTION: Programming and layout track must not exceed
16V when using this decoder.
Installation Instructions
1. Carefully remove the locomotive shell.
(Figure 1) Note the orientation to
the frame for correct re-installation.
Arrange internal wires to expose the
jumper board in the locomotive.
2. Remove the jumper board from the
locomotive’s 21MTC pins. (Figure
2) The jumper board allows the loco
to operate on a standard DC track or
in analog mode on a DCC track. If
the loco also has a 8pin NMRA
socket, any jumpers should also
be removed.
3. Insert the 21MTC socket onto the ex-
posed pins. The black socket and the
decoder text should be facing up. The
socket is indexed so it will only t on
in one conguration. (Figure 3) Seat
the decoder rmly on the pins.
4. Replace the loco shell on the frame.
The loco is now ready to run on your
DCC system using the factory set
address 03. See next page for cus-
tomizing some of the functions of the
DH126MT decoder.
Figure 1: Remove loco shell
Figure 2: Carefully
remove jumper board
Figure 3:
Carefully plug in decoder
Jumper Board
Decoder

© 2016 Digitrax, Inc. www.digitrax.com— 3 —
Installation Notes
1. Do not exceed the decoder’s 500mA total function output rating.
2. We recommend that the Blue wire, also called +Common or Lamp Common,
be connected as shown. If you wish to omit the Blue wire in your installation,
consult the Digitrax Decoder Manual for more information.
3. The head lamp should be hooked up using the Blue/+Common wire for opti-
mal Digitrax transponding operation.
4. To use a function output with an inductive (coil) type load, see the Digitrax
Decoder Manual for more information to avoid damage to the decoder.
5. See the Digitrax Decoder Manual for full details of wiring 12-16V lamps, 1.5V
lamps, and LEDs. Lamps that draw more than 80 mA when running require
a 22 ohm 1/4 watt resistor in series with the directional light function lead to
protect the decoder.
6. Some locomotives employ lter capacitors for RFI suppression in the loco-
motive wiring. These may cause problems with Supersonic decoders and
non-decoder analog operation on DCC. This capacitor should be removed for
safe operation.
Customizing Your Decoder
Your Digitrax decoder is ready to run and will operate using address 03 with no
additional programming. For a more prototypical railroading experience, your
decoder can be customized for your specic locomotive by programming some of
the Conguration Variables, or CVs, available. See the Digitrax Decoder Manual
or the Digitrax web site for more information.
Changing the Decoder Address
The rst CV most people change is the decoder address. This allows you to inde-
pendently control each loco with a unique address. Digitrax decoders are shipped
with CV01 (AD2), the two digit address, set to 03. Following is a brief description
of how to change the decoder address with a Digitrax DT4XX series throttle. See
your Starter Set Manual for complete programming instructions.
1. Place the loco on the programming track not to exceed 16V. Go into
Program Mode on your system. On DT4XX throttle press PROG.
2. Choose AD2 for 2 digit addressing or AD4 for 4 digit addressing.
3. Choose the address you want to set up for the decoder.
4. Complete address programming by pressing ENTER.
Note: CV29 must also be programmed to enable 4 digit addressing, this is done
automatically by the DT4XX throttles. See your Digitrax Decoder Manual or the
Digitrax Toolbox App for how to set up CV29.

© 2016 Digitrax, Inc. www.digitrax.com— 4 —
Digitrax LocoMotion®System
Your locomotives look like the real thing, now you can make them run like the
real thing, too. Digitrax decoders incorporate torque
compensation for smooth as silk operation. You can also program CVs that
control momentum, 3 step and 128 step speed tables, switching speed, normal
direction of travel, scalable speed stabilization and more to take full advantage of
the Digitrax LocoMotion System.
Momentum-CV03 & CV04
Momentum is part of the LocoMotion System. Acceleration is controlled by CV03
and deceleration by CV04. Both come from the factory set to 000. A range of 000
to 031 is available for both accel and decel. Try CV03:003 and CV04:000 as a
starting point for experimenting with momentum.
Speed Tables-How the Loco Responds to the Throttle
With Digitrax LocoMotion, there are two types of speed tables: 3 Step Tables and
High Resolution 28 Step Tables. Please see your Decoder Manual for a discussion
of the 28 Step Tables. The 3 Step Tables are set up by programming 3 CVs: Start
Voltage (CV02), Mid point Voltage (CV06) and Max Voltage (CV05). These values
are set at 000 at the factory. All have a range of values from 000 to 255. We rec-
ommend the following CV values as a starting point for experimenting with speed
tables.
Loco Type V Start
CV02
V Mid
CV06
V Max
CV05
Switcher
Concentrated low speed. Limited top
speed
002 038 064
Road Switcher
Prototypical top speed w/evenly
distributed curve from 0 to top speed
002 048 098
Mainline Loco
Quick increase to cruising speed then
levels o to prototypical top speed.
002 128 154
Decoder Reset CV08
Decoder reset lets you reset all CV values to the initial factory settings. To reset all
CV values, program CV08 to a value of 008. You also have the option of reset-
ting all the CV values except the 28 speed step tables and CV60 selected sound
scheme. To do this program CV08 to a value of 009.

© 2016 Digitrax, Inc. www.digitrax.com— 5 —
Other LocoMotion®Features: Switching Speed, Normal
Direction of Travel & Scalable Speed Stabilization
(Back EMF) Features
Switching speed is controlled by CV54. The factory setting is 000 for OFF. To
turn on the switching speed feature, program CV54 to a value of 001. When this
feature is on, use F6 to activate and deactivate switching speed. With the feature
on the throttle’s target speed is eectively reduced by about 50% and the eects
of accel and decel programmed into the decoder are reduced by 1/4. This is useful
for yard switching operations.
Normal Direction of Travel is controlled by CV29. See your decoder manual
or the Digitrax Toolbox App for additional information on the settings for CV29.
The intensity, or droop, of Scaleable Speed Stabilization (Back EMF) is
controlled by CV57. The factory setting for this feature is 006 which is suitable for
most locos. You can adjust this value in the range of 000 for OFF to 015 for the
maximum eect. Consult your Digitrax Decoder Manual for info about CVs 55 &
56 and their eects on scaleable speed stabilization.
SuperSonic Silent Operation and Torque Compensation
The factory settings in the decoder provide silent, smooth operation of your loco-
motive under most conditions. For more information about these settings, please
see the Digitrax Decoder Manual or our website.
Digitrax Transponding CV61
Digitrax Transponding is controlled by CV61. The initial factory set value is 000
for OFF. To turn on transponding, program CV61 to a value of 002. This al-
lows you to use Digitrax transponding to keep track of your rolling stock. When
transponding is enabled, the front light of the locomotive will icker slightly to
indicate transponding signal is being communicated.

© 2016 Digitrax, Inc. www.digitrax.com— 6 —
Function Outputs on the DH126MT
The DH126MT is set up at the factory to control two function outputs. The
DH126MT is congured to control the lights on the factory light board through
the 21MTC interface using Function 0 (FOF-forward and FOR-reverse) for direc-
tional lighting.
Function Remapping
Function remapping allows you to program the function outputs of your decoder
to be controlled by selected function keys on your throttle. Please consult the
Digitrax Decoder Manual or website for information on function remapping.
Warranty & Repair
Digitrax gives a one year “No Worries” Warranty against manufacturing defects
and accidental customer damage on all Digitrax command stations, boosters,
throttles, decoders, power supplies and layout control devices.
That’s it! A simple, straightforward warranty with no tricky language!
Visit www.digitrax.com for complete warranty details and instructions for
returning items for repair.
Please return warranty items directly to Digitrax - DO NOT return items
to place of purchase.

© 2016 Digitrax, Inc. www.digitrax.com— 7 —
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Available
Computer Interface
Decoder Programmer
Sound Programmer
TM
E
MPIRE
B
UILDER
Super
TM
0 0 0 0
2443 Transmitter Road
Panama City, FL 32404
www.digitrax.com
Need Support?
helpdesk.digitrax.com
DH126MT
Fits Many HO Locomotives
Made in the USA
TM
Part 15, Class B
RFI Compliant
307-1016-0000