SFX0416 1 Amp HO/N SoundFX & Function Decoder


Wired Mobile Decoder with SoundFX® & FX3 Function for most HO and many N scale Locomotives.

Preloaded with selectable generic steam and diesel sound schemes

Visit Digitrax Sound Depot to learn how to customize the sound project that is included with the decoder and how to download different sound projects.

Includes 28mm 8 Ohm Speaker & 330uF Capacitor

Please Note: The SFX0416 has no motor functions and is used in conjunction with a standard mobile decoder to add sound and additional funcitons to the locomotive.

Regarding N Scale applications:

Although the SFX0416 decoder PCB is physically small enough to fit into many types of N Scale rolling stock and dummy locomotives, for N Scale applications the standard 28mm speaker must be replaced with a smaller speaker and installation of the capacitor can be omitted.

Finally, the SFX0416 is an 'add-on' type SoundFX decoder, meaning it works with a standard DCC motor decoder in locomotive applications. N-Scale locomotives generally do not have the necessary space for both the SFX0416 and a motor decoder inside the locomotive.  To use this sound and function decoder as an add on to an existing mobile decoder in an N Scale locomotive, you can install it in an N Scale car that runs behind the locomotive. If you are installing a sound decoder in a locomotive that does not already have a mobile decoder, one of our N Scale motor, sound & function decoders would be the best choice for N scale locomotive installations. 


Current Rating-Motor
Not a motor decoder
1.22” x 0.42” x 0.21” (31mm x 10.6mm x 5.3mm)
Wired (read more)

Decoders with wires provided for hooking up the decoder in the locomotive.  If wires are not provided for hooking up functions, solder pads are provided to allow you to access those functions by adding wires. 

Digitrax Mobile Decoder Wire Colors

What the wires are for

Wire Color

Power Pick-up Right   (Engineer's Side)


Power Pick-up Left   (Fireman's Side)


Motor + Right Brush


Motor – Left Brush


F0(Fwd)-Forward Light


F0(Rev)-Reverse Light


Lamp Common


F1-Function 1


F2-Function 2


F3-Function 3


F4-Function 4

White w/ Yellow   Stripe

F5-Function 5

White w/ Green Stripe

F6-Function 6

White w/ Blue Stripe

Note: DH82 & DN92 decoders, some of the very first decoders produced by Digitrax used a different wiring color code.  Please check decoder spec sheets for the wire colors that were used with these decoders.

Function Outputs
4-200mA (read more)

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

The combined current available for these four functions is 200mA.

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
FX3 (read more)

Digitrax Real FX3

  • Turn functions on and off. 
  • Head lights and tail lights are automatically reversing unless you make them independent. 
  • All function outputs have FX generators for prototypical lighting effects and have qualifiers for FX effects and qualifiers for standard on/off functions.
  • All Digitrax Series 3 decoders have FX3 type functions.
  • FX3 decoders offer full function mapping so you can choose which function (F0-F12) controls each function lead.
  • FX3 decoders offer master light switch capability.
  • FX3 decoders offer qualifiers for FX function operation qualified by one of the following:  the loco's direction of travel, whether F0 is on or off, loco direction and F0, or whether the loco is moving or not. These qualifiers are also available on function outputs that are used as standard on/off functions.

Motor Isolation Note:  FX3 decoders have motor isolation protection. If the decoder senses that the motor is not isolated, it will not run the motor. In this case, you will be able to control the loco’s functions but the motor will not work.

Here is an explantion of how the CVs that control FX3 effects work.  Most modern Digitrax systems do not use hexadecimal format but it is provided here in case you need it for older systems.

CV 49-52, CV113-116, CV62 & 63: Digitrax Real FX3 Special Light Effects

Decoders with FX3 features have 8 user configurable, independent special effects generators.  These are set up by programming CV values as described below.  If your decoder is not a “series 3” decoder, please check the spec sheet to determine which type of functions it supports.

FX3 functions incorporate FX generators with additional dynamic and static qualifiers.  FX3 functions are fully remappable so they can be controlled by any function key on your system.  A master light switch can be set up to turn off all lights on a locomotive. Functions associated with advanced consists can be controlled, too.

Setting Up FX3 Effects On Function Outputs 

1. Each function output has an FX3 control CV associated with it. Using TABLE IVa below, determine which CV you need to program to set up an FX3 feature for the function output you are working with. For example, if you want to set up an FX feature on your forward headlight, you will use CV49 to control the FX3 feature for the lamp attached to F0F. Some decoders do not have function output wires attached. See the specific decoder instructions to determine which "pad" on the decoder controls each function. Use thin wire or wire saved during previous decoder installations to solder function output wires to the pads associated with the function you want to use.

 TABLE IVa:  FX3 Generator CVs  



Function #

Output Color


F0/Light Forward (F0F)



F0/Light Reverse (F0R)



F1 Function 1



F2 Function 2



F3 Function 3



F4 Function 4



F5 Function 5



F6 Function 6


 NOTE:  Decoders with FX function generators use different CVs to control function outputs.  Click here to go to FX page.  CV53 & CV54 are not used for FX3 control.     

2. Each FX3 effect has a CV value that generates the effect you want and controls how the effect works with respect to locomotive direction and the head light (F0) function.

The FX3 CV value is made up of 2 digits. The second digit determines which FX3 effect will be generated. The first digit determines how the effect will work with respect to the locomotive direction, the head light and other functions. Use TABLE IVb to determine the second digit and Table IVc to determine the first digit of the FX3 CV value to program into the CV selected in step 1.

  TABLE IVb:  The Second digit of the FX/FX3 CV value determines which FX3 effect will be generated.

FX3 CV   value second digit (hex)

FX3 effect generated


No effect, normal function control of lead


Random flicker 


Mars light


Flashing head light


Single pulse strobe


Double pulse strobe


Rotary beacon simulation




Rule 17 dimmable headlight, dim   when F4 is active or locomotive direction is opposite normal direction of   travel (NDOT)


FRED or "end of train" light


Right ditch light on when loco is running forward and F0 is   on.  When F2 is on, the right ditch   light flashes alternately with the left ditch light to simulate ditch light   operation at a grade crossing.


Left ditch light. on when loco is running   forward and F0 is on.  When F2 is on,   the left ditch light flashes alternately with the right ditch light to   simulate ditch light operation at a grade crossing.


Digitrax reserved for effects expansion.


TABLE IVc  The first hex digit of the FX3 CV value determines how the effect generated will behave. For example, two strobe lights can be set up to flash alternately by setting one to phase A and the other to phase B. The strobes can also be set up to be on when the loco is moving forward and off when moving backward.

TABLE IVc:  How FX3 effects generated will work 

FX3 CV   value first digit (hex)

How the FX3   effect generated will work


Forward direction, ON with function ON, effect phase A


Reverse direction, ON with function ON, effect phase B


Non directional effect, ON with function ON, effect phase   A


Non directional effect , ON with function ON, effect phase   B

4x* Master Light Switch F0

Forward direction, ON with F0 ON & function ON, effect phase A

5x* Master Light Switch F0

Reverse direction, ON with F0 ON & function ON, effect phase B

6x Master Light Switch F0

Special Logic for Fwd Ditch Light or Rule 17 dimming    Standard Ditch Light Operation

7x Master Light Switch F0

Special Logic for Rev Ditch Light or Rule 17 dimming    Standard Ditch Light Operation

FX3 CV value first digit (hex)

How the FX3   effect generated will work


Speed=0, non directional effect, phase A and function   qualifier


Speed>0, non directional effect, phase B and function   qualifier

Ex Master Light Switch F0

Ditch off phase A  Alternate Ditch Operation-Off when running flash on with   F2

Fx Master Light Switch F0

Ditch off phase B  Alternate Ditch Operation-Off when running flash on with   F2

3. Program the FX3 CV value from step 2 to the FX3 CV identified in step 1. If you are using the PR1, an FX set up section is available where you can just "point and click" to set up the effects you want to use. The software lets you select which function output and which FX feature you want from a menu so you don' have to use the tables above to determine which CV or CV value to use. 

4.  For FX3 decoders, you can set up as many as 8 function outputs. All FX3 outputs can be set up with FX3 effects. 

5.   If you want any function output to remain a simple on/off output, leave it programmed to the factory default of CV value 00.      

Customizing FX3 Effects-Rate and Keep Alive: CV62 

CV62 lets you control the rate and keep-alive brightness for each FX3 effect you set up. The CV value for CV62 is made up of 2 digits, the first digit and the second digit.

The first digit controls the keep alive/baseline off voltage for incandescent lamps. This value should be between 0 and F. A value of 0 gives no keep alive and a value of F gives maximum keep alive. Values between the high and low allow you to vary whether the lamp actually goes off between light pulses or whether it stays on very dimly or more brightly. (If you are using LEDs, the first digit for CV62 should be 0.)

The second digit controls the rate of the FX3 effects programmed. This value should be between 0 and F. A value of 0 gives a fast rate and a value of F gives a slow rate of operation. We recommend you start with a 4 and adjust it up or down until you get the effect you are looking for.

Ditch Light Hold Over Time CV63

If you are using the ditch light effect in conjunction with F2, CV63 lets you set up a hold over time to control how long the ditch lights continue to blink after F2 turned off by releasing the key on the throttle. Remember that F2 is a momentary key on most Digitrax throttles that will keep function 2 on as long as you hold the key down and then turn function 2 off when you release the key. This allows the ditch lights to be on steady during regular operation and to begin alternate flashing when F2 (usually the horn) is activated and to continue flashing alternately for a predetermined length of time after F2 is released; just like the prototype. A value of 00 yields no hold over time, a value of 40 yields a realistic time of about 5 seconds. A value of 255/xFF yields about 20 seconds hold over time.

FX3 Examples

Any function output on the decoder can be set up for any FX3 effect by programming its associated FX3 CV to the appropriate FX3 CV value. For example, if CV52, the FX3 CV for F2, is programmed with an FX3 CV value of 002/x02, the violet F2 function output will be a Mars light when F2 is turned on for this decoder address and the decoder's direction is forward.


CVs that affect all FX3 function outputs 



CV# & CV Value


Effect on Decoder

Analog Functions Enable/Disable

(Not applicable for FX3)

13: 207/xcF

All functions F0 though F4 are ON in analog (DC) mode

Configuration Register


Advanced 28/128 speed step mode, analog mode conversion   enabled

Keep Alive/Rate


High keep-alive for lamps, Rate 4 for approx. 1 sec FX   effect rate

Ditch Light Hold Over Time


5 Sec Ditch light holdover after F2 is turned OFF

 CVs that affect specific FX3 outputs:



CV# &CV Value


FX3   Effect Generated

F0 Fwd White


Rule 17 dimmable headlight,   directional

F0 Rev Yellow


Normal directional reverse headlight, NO effect used

F1 Green


Right Ditch light, directional.  F0 & F2 must be ON for this to operate.

F2 Violet


Left Ditch Light, directional.  F0 & F1 must be ON for this to operate.  

F3 Brown


MARS light, ON when F3 is   ON  (If we used {113:050/x32} we would   get opposite phase MARS light)

To set up two alternating double pulse strobes on the green and violet function outputs controlled by turning on both F1and F2, program CV51 to a CV value of 037/x25 and program CV52 to a CV value of 053/x35. This is an example of using the alternate effects phases A & B.

For FX3 decoders you have 8 FX3 generators available to use with your function outputs.

Setting Up Static (Non-FX3) Functions with FX3

When an FX3 decoder output is set up for static on/off operation (no FX3 effect), you can use static qualifiers to customize the operation of the on/off function of that output.

In this case, the second digit of the FX3 control CV will always be 0 to set the decoder for static (no FX3)function operation. The first digit is determined by the following table according to how you want it to work.

Static CV value

How The Static Function   Output Will Work


On/Off   Output controlled by function map


On/Off   Output controlled by function map


Forward   qualified On/Off Output


Reverse   qualified On/Off Output


F0   qualified On/Off Output (Master Light Switch F0)


F0   qualified On/Off Output (Master Light Switch F0)


F0   On in Forward Direction qualified On/Off Output (Master Light Switch F0)


F0   On in Reverse Direction qualified On/Off Output (Master Light Switch F0)


Speed=0,   non directional qualified On/Off Output


Speed>0,   non directional qualified On/Off Output

Troubleshooting FX3 effects

Common problems with FX3 set up are:

Trying to program a decoder for FX3 when the decoder does not support FX3. Be sure the decoder you are programming has FX3 features. Digitrax introduced FX3 in 2002 in the “series 3” decoders. Digitrax introduced FX in the summer of 1995 in all of its premium decoders so if your decoder was made before then it does not have FX capability. FX & FX3 decoders use different CVs for controlling the function outputs of the decoder.

FX3 effects don't work as expected. Review the qualifiers you set up for the effect. For example, if the effect is set up to come on only when F1 and F0 are active and the loco is headed in the forward direction, be sure you have met those conditions.

Setting Up A Master Light Switch with FX3 Decoders

For FX3 decoders F0 can be used as a master light switch to turn off all lights in the locomotive when F0 if OFF.  To do this set up all functions qualified to be on when F0 is on and off when F0 is off.  See Table IVc above and use 4, 5 ,6, 7 ,E, or F as the first digit of the FX/FX3 control CV to enable the master light switch on F0.

8 Ohm 28mm round
Simultaneous Voices
Onboard Sound Memory
16 Megabit
No Worries Warranty (read more)


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!

Repairs are simple, too!  Just fill out the form and return your items directly to Digitrax for repair.  We'll get them fixed up and return them to you as quickly as possible.  Please DO NOT return items for repair to the place of purchase.

Make Sure Your Item Needs To Be Repaired Before Sending It To Us!  Many of the units we receive for repair do not need any repairs at all. Before you send any units for repair, please take a few minutes to review our Support Options.

1.  Check the Tech Support Depot for help.  Search for troubleshooting guides.

2.  Click here to send Digitrax Tech Support a message.

Please give your name, e-mail address, phone number and when is the best time to contact you.  Please give a complete description of the issue you are having.

Many problems are easily resolved by contacting Digitrax Tech Support without having to send in your unit.

Note: Some Digitrax products are no longer repairable due to unavailability of repair parts. Un-repairable items will be returned to you at no charge with no repairs made.

Please Note:  Most of our products are not user serviceable. If a defect or accidental damage occurs, return the unit directly to Digitrax for service.  Please do not open the Command Station/Boosters (except for making voltage adjustments or changing batteries per the manuals).  Please do not remove the shrink wrap protective sleeves from the Digitrax decoders. Shrink may be peeled back to expose pads for adding function wires. 

Accessory items that are not covered under the No Worries Warranty carry a 90 day warranty against defects in materials and workmanship.  This includes speakers, wire, cables, battery covers, etc.

Intentional damage and customer modifications outside the scope of instructions provided with the product are not covered by this warranty. 

Do NOT send a locomotive with your decoder. If a locomotive is sent to Digitrax, Digitrax will ship the entire package back, unrepaired.