DH120D 1 Amp Digital Command Control Mobile Decoder

This product has been replaced by the 1.5 Amp Economy HO Scale Mobile Decoder (DH123D) and is no longer available. Click here to view the DH123D.

1.0 Amp (1.5 Amp Peak) Mobile DCC Decoder with 9 pin plug, also available as DH120P with DCC medium plug, DH120PS with short DCC medium plug, and DH120AT with Athearn Clips

Retired in 1998


Current Rating-Motor
1.0 Amp (1.5 Amps Peak)
0.67” x 1.0” x 0.18” (17.02mm x 25.4mm x 4.57mm)
Wired, DCC medium plug, Athern Clips
Function Outputs
2 (read more)

2 function decoders support F0 Forward and F0 Reverse.  This allows for reversing headlights or for two separate functions.

How functions are numbered:

F0 (FWD) White

F0 (REV) Yellow

The Blue wire is Lamp Common to allow for continuous lamp operation.

F1 Green

F2 Violet

F3 Brown

F4 White with Yellow Stripe

F5 White with Green Stripe

F6 White with Blue Stripe




and so one are each counted as one function.  This is an industry wide convention. 

Function Type
Standard (read more)

Standard functions turn functions on and off. Many Digitrax decoders with standard functions offer head lights that can be set up to be either automatically reversing or individually controllable.  Digitrax decoders are shipped with automatic reversing head lights enabled.  When you are using a standard function output, simply hook up the function output to the function device and you will be able to turn it on and off from your throttle.

Series 1 (read more)

Digitrax Decoder Series Numbers

Over the years as technology advanced, Digitrax has added more and more features to our mobile decoders.  Also, over time, the industry standards and uses of come CVs have changed.  Each of our decoder web pages includes a link to a specification sheet for that particular decoder so that you will know which CVs are used for which features in that particular model.

Digitrax uses series numbers to let customers know which feature set is part of a particular decoder.

The fifth character of each mobile + function decoder part number is the Digitrax series designator.  For sound + motor + function decoders we typically use the sixth character as the series designator.  There are variations in a few part numbers.

Series 6

Compatible with Digitrax PX series Power Xtenders to keep locos and sound running in the presence of dirty/poor track work.
FX3 outputs optimized for both LED and bulb applications.
FX3 outputs have configurable pulse available on all outputs.
Improved Scaleable Speed Stabilization (BEMF).

SoundFX Series 6 Features

Sound decoders available with either 8 bit standard or 16 bit premium sound.
Sound decoders configured for 8 Ohm speakers.
Allows for longer sound fragments.
Available in either standard 3 or premium 4 voice versions.
Auto CV configuration by sound projects
Scaleable Speed Stabilization (BEMF) optimized for sound operation.

Series 5

Sound Bug Compatible:  Series 5 Digitrax Decoders add the ability to add sound to regular mobile decoders with Sound Bug.  Some Series 5 decoders have sockets for simply plugging in the Sound Bug while others require soldering to wire the Sound Bug to the decoder.

Series 4

First generation SoundFX decoders

Most are mobile, sound and function decoders, some are sound and function only decoders.

Series 3

Series 3 decoders with 6 functions have FX3 function outputs

Torque compensation

SuperSonic motor drive for quiet operation (silent operation)

Support for all DCC programming methods as of the time of release

Operations mode read back capability for CV read back on the main line

Scaleable Speed Stabilization (Adjustable Back EMF)

One Step decoder Factory CV reset (CV08=8 or CV8=9 to preserve loadable speed tables)

Motor Isolation Protection


White or Golden Yellow LEDs on decoders that come equipped with LEDs

Series 3 decoders with less than 6 functions have a modified set of features

Series 3 Economy

Digitrax Decoders have all Series 3 features EXCEPT Scaleable Speed Stabilization (BEMF)

Series 2

FX function outputs

Scaleable Speed Stabilization (Back EMF)


Series 1

Digitrax decoders have standard or configurable strobe function outputs.

Replaced by
Current Rating-Functions