No G scale decoders, I use these in Z scale

I'm still on the fence with these decoders, The advantages I was given was small size and the ability to run the high current motors like Marklin without surging.

Well, the surging issue is true, I tried a TCS decoder on a Marklin mikado and it jumped and bucked like a wild horse, while the CT decoder controlled it fine (as long as you tune the BEMF parameters).

And they are indeed small, they now make the smallest decoder in the world, BUT there are compromises!

Also their sound cards are indeed tiny, but the programming software is crap, Yes, crap. I still cannot get it to work right, it runs on DOS, and I've got 45 years in the software industry.

I'm figuring it out, and these guys in the UK seem to got some stuff working with thier own software:


Another good reference is the website of Arnold (Huebsch?).  http://amw.huebsch.at  There is a lot of CT Elektronik stuff there, also known under the name of Tran, since Tran seems to be the name of the manufacturer.

 He also has some errant forum sites, one for Zimo: http://zimoforume.huebsch.at/default.aspx but it's basically dead, no one really keeps it up.


List of decoders:

DCX74 - a little larger than the preferred DCX75

13 x 9 x 1.5 mm (LWH) - Motor and 4 function decoder - medium sized, nice if you have room

Here is an english translation of the manual: http://www.tran.at/Dokumentation/DCX74_en%20long.pdf

DCX75 - very small motor only decoder

The DCX75 is a very small decoder, 1 amp, 2 function, 11 x 7.2 x 1.4 mm, the thinnest and pretty much the smallest Z scale decoder.

A good choice for Marklin Mikado / Pacific

You can tune the P and I parameters in the BEMF, there are different frequencies for the motor drive, and it has a user speed curve.

It comes in several models, but for Z scale, just get the plain one with the wires soldered on.

Voltage range is 7-18 volts, 250 mz on the function outputs total.

Unfortunately, all documentation seems to be in German.

Connections: standard colors

  • orange - motor right
  • gray - motor left
  • red - right rail
  • black - left rail (note common for lights is the black wire)
  • white - front headlight
  • yellow - rear headlight

DCX76 - even smaller, 4 function

0.8 A Micro decoder, 4 enhanced functions (10.8 x 7.1 x 1.3 mm) LxWxH

Here's a picture of the new DCX76, decoder, currently the world's smallest:


DCX77L - smaller and skinny

Dim. 9.5 x 4.0 x 1.8 mm / L x W x H


DCX77Z - smallest in the world

Dim. 7.6 x 5 x 1.8 mm / L x W x H

Rail voltage 10-16 V
Maximum Motor Current - Peak (3 s) 1.2 A
Maximum engine power - Duration 0.8 A
Maximum current of the function outputs 200 A
Maximum total current of the decoder - Duration 0.8 A
Dimensions (L x W x H)  
Operating - 20 to + 80 C

The DCX77z is only 7.6 x 5 x 1.8 mm in size and can therefore be installed in many Z and N Locomotives without complex milling work. The leads are highly flexible stranded wire color-marked.

GE70 sound decoder

24 x 9 x 3.5 mm - 0.

-24 x 9 x 3.5 mm- sound and xx function decoder - seems to be replacement of ge75 - used to be different size now seems to be depopulated SL75 - 21 x 15 x 3.7 mm

Below is the the picture of the GE75 on the CT Elektronik site: (the picture does not match the pictures in the manuals for the GE70 or GE70-2)



Here's here is the decoder I received, that was marked GE70/DA: (notice the missing two chips on the bottom left corner)

It came with a small rectangular speaker, with a small clear plastic sound box. Dimensions are 11.25 mm wide by 15.2 mm long by 9 mm high

The sound from the speaker was just amazing. Loud, undistorted.

The sound decoder seems to want a 50 ohm speaker, to use an 8 ohm speaker, you need to add a resistor in series.

GE75 sound decoder

24 x 9 x 3.5 mm - sound and 2 function decoder,  Maybe this is obsolete now? Below is the the picture of the GE75 on the CT Elektronik site: (the picture matchs my GE70 unit except for having two more chips on the lower left corner. Maybe this is the picture of a motor and sound decoder, since you can see the extra leads for the motor.


GE75 description (translated from CT Elektronik site):

1 watt output for sound, 3 channels simultaneously callable 16Mbit sound memory (about 170 sec.) 16Bit sounds

  • Freely programmable in use with SoundProg, *. wav 11kHz or 22kHz, 8 or 16 bit sound
  • Up to 8 sound parameters separately callable
  • 3 Channel Sound (simultaneously play sound sequences of 3)
  • Läutstärke separated individually controlled by CV (to increase the contrast sound)
  • 1 Watt continuous output short circuit protected
  • 16Mbit (200 Sec) Sound memory (OGM or sound scenes)
  • Two random number generators (stationary and while driving)
  • Free choice of number of cylinders (2 cylinders, 3 or 4 cylinder)
  • Synchronization over the reed switch, hall sensor or internal speed curve
  • Frequency-dependent sound change (simulation of the cylinder size, when the clutch)
  • All sound functions moved freely on and off NMRA function mapping or by extended mapping of CT 

new features 4 Generation

  • Sounds 22kHz or 11kHz Sounds, 8 or 16 bits Sounds
  • DA-converter for improved sound quality
  • Digital amplifier instead of analog amplifier (to reduce heat generation)
  • 126 sound-slots for the acceleration of the diesel or electric sounds
  • 126 slots for the constant sound speed of the diesel or electric sounds
  • 126 sound-slots for the shutdown of the diesel or electric sounds
  • 6 sound slot in addition, between the driving noise (eg switching operations)
  • Bidirectional Communication (Bidi) prepared
  • Brakes by asymmetric signal (brakes with diode)
  • 5V output for low voltage lamps, pads for power capacitor
  • 2 reinforced functions depending 250mA
  • Automatic adjustment of the braking sequence
  • Automatic release of brake sparks (random flicker)
  • The right speaker has dim. von 15x11x8 mm including resonator


24/9/3.5 mm (L/B/H)

Functions as delivered:




4 - from power up, makes a hiss, hit again, some popping and then back silent

5 - whistle

6 -coal shovelling - continuous

7 - short hiss - probably unintentional

8 - starts sounds air pump

9 - needed to allow chuffing


seems that 8 and then 9 needs to be done in sequence


CV definitions

(interestingly enough, selecting the documentation for the GE70, the web page is http://www.tran.at/Produkte/GE75.shtml )


1, 2, 3, 4, 5 all standard (note: CV1=0 is hard reset! It takes a while to execute, so be patient)

6 - mid speed

7 - version number

8 - manufacturer id (should be 117)

9 - motor control period 20-150 hz, default 141

17, 18, 19 - standard


CV 49

= 0 factory default for 4 cylinder steam engin

bit 0 = 1 prescaler for reed-contact for sync as a function of CV133

bit 1 = 1 diesel-electric

bit 2 = 1 2 cylinder loco

bit 3 = 1 3 cylinder loco

bit 4 = 1 no steam bursts during mountain-from trips (only idle noise)

bit 5 = 1 evaluate LGB pulses from F1 (serial functions?)

bit 6 = 1 no noise between standstill - trave (pipe)

bit 7 = 1 no sound btw trip - nursing resistance (braking)


bit 0 =1 enables the prescaler for pulses

CV133 is the number of pulses per chuff, i.e. CV133=10 means 10 pulses makes one chuff.




Sound programming

The "*" marked sounds are played endlessly, depending the operating state, typically the road noise and stop-
noise. The other functions can be free-function keys will call. The manual noise is also repeated, Solan- GE, the corresponding function key is pressed. The number of repetitions the individual sounds are of CV122-128 Bit 5,6,7 also dependent. Each- Line forms a sound group (slot), of course, not all A- contributions of a group are filled. The assignment is to NMRA function mapping CV33-CV48.


By noise during acceleration *

Drive-by constant pace *
04: 04:TAKT1-m.WAV TAKT1-m.WAV
05: 05:TAKT2-m.WAV TAKT2-m.WAV
06: 06:TAKT3-m.WAV TAKT3-m.WAV
07: 07:TAKT4-m.WAV TAKT4-m.WAV

Moving vehicle while braking *

Gimmicks to 0 to 3 (hissing steam from an impact)

Gimmicks to 4 to 7 (hissing steam from an impact)

Gimmicks to 8 to 11 (hissing steam from an impact)

Start noise (transition from "sound off" to "stand still")
16: 16:--- ---
17: 17:--- ---

Abstellgeräusch (transition from "stagnation" to "sound off")

SL75 Motor and sound decoder

24 x 9 x 3.5  - motor, sound and 4 function decoder - probably the smallest motor & sound decoder made


15.0 x 9.5 x 2.7 mm LxWxH


Using the decoders:

I put one in a Marklin 0-6-0 tank engine, ran spurts, something wrong.

Documentation was not right, especially CV9..

OK, you MUST use DIRECT MODE to program the chip, don't try anything else. This means you Don Fedjur! tongue-out

CV1 = 0 does execute a factory reset. I have used it a couple of times. It takes a while to respond.
CV109 can be useful in allowing access to alternative CV range (basically have two full sets of CVs which are swapped by CV109). Its worth setting CV109 to an odd number to gain access to the second set, fiddle with those for a while, and if still stuck, then go back to the first set by setting the value to an even number (0). That seemed to fix some of the wierdness in mine, though still not 100% happy that I understand what is going on.

CV116: Half speed in reverse is caused by bit 2.

To make decoder work satisfactorially in my 060, I ended up with:

CV5 = 255
CV6 = 84 Wanted low speed range to be more controllable, hence somewhat skewed downwards, couldn't make a custom speed table behave to my satisfaction, but suspect some of the JMRI files may be screwed and ran out of time.
CV29 = 1 (guess who wired the chip to motor leads without checking !!).
CV50 = 255 (regulation influence, standard value)
CV51 = 30 P-value (much reduced from default)
CV52 = 15 I-value (kept in proportion to CV51, seemed to be OK, so stopped fiddling).
CV64 = 200 ( cuts top speed, see the Arnold Web Commentary on the Trans decoders and note below)
CV116 = 3 (Half speed operates on F3, reverse speed is normal, bit 3 can give 65% reverse speed)

If it keeps surging, keep raising cv51 up to 255... keep cv 52 about half of cv 51.

A vast resource is Arnold's Modell WEB: http://amw.huebsch.at/ - be sure to click the American flag in the upper right corner

Here is a document from Arnold that explains some general stuff on CT decoders: http://www.elmassian.com/images/stories/dcc/ct_elektronik/TranKommentare.pdf

Note: I can use help on translating... one current "mystery" is the use of the word "clutch", "digital clutch"... it seems related to functions being toggled on or off, or perhaps a momentary function and the duration. It also might be related to a chuff trigger inputs.

CV 1 - short address, default 3, can be set to 1-127, apparently setting CV1 = 0 does a full reset.

CV2 - normal, start  "voltage"  0-255

CV3 acceleration

CV4 deceleration

CV5 max speed (0-255)

CV6 - mid speed voltage (0-255), set to zero if you want a linear speed curve between CV2 and CV5..

CV7 - version number

CV8 - manufacturer number (117)

CV9 - sets motor drive frequency (default 134, value range 13-63 and 134-191) Values of  13-63 correspond to 30-150 HZ, and values of 134-191 corresponds to 16khz to 10khz??

CV13 - analog mode - seems to determine if outputs A1 through A8 are on when running on DC

CV's 17 & 18 & 19  - standard DCC

CV29 - standard DCC (appears that DC mode is off by defuault)

CV30 - troubleshooting - read back only, 1=motor? 2=light,  3 = light/motor have a short

CV's 33-46, 163-176 - function allocation

CV50 -  BEMF control?

CV51 - BEMF P value

CV52 - BEMF I value

CV53 - decoder lock

CV54 - lamp dimming

CV55 - diming output coupling


56 switching time of the clutch output

57 dimming mask

58 - dim mask 2

59 - "L" speed selected for L section

60 - "U" speed selected for U section

61 - has to do with the HLU

64 - control reference? friving ability

67-94 - user speed table

154-161 lighting effects for output a1 through a8 (a1 is white, a2 is yellow, a3 is green, a4 is purple)

0 = no effect (on solid)

1 = flashing / blinking

2= alternate flashing

3= single pulse strobe

4= double strobe

5= flashing headlight between max and PWM value of CV114

6= left ditch light - brightness between max and PWM value of CV114

7= ditch light right

8= rotary beacon

9= gyralite

10= mars light

11= soft start






CT Electronik programmer - hardware


The sound programmer is referred to as the "new" one.


At the right side, there is a connector to go to the programming track. I doubt it matters, but the upper terminal is referred to as the right (red) rail, and the lower terminal as the left (black) rail.

Below that is a yellow led. (don't know what it signifies, lights when power is applied)

Just above the large capacitor (the silver disk ringed with brown) is a white led. (don't know what it signifies yet)

The serial port is on the upper right side, and the power connector is on the lower right side.

The power input is defined as 14-16 volts, ac or dc is not specified, but looking at the 4 diodes to the right left of the connector and below the cap, that's a full wave bridge setup, so the 14-16 volts must be ac (or DC). I powered mine with a regulated supply set to 15 volts, it draws 40 milliamperes.

Warning in the manual:

"All of the sound decoder outputs are not protected against overcurrent. There are no protective measures against internal and external short-circuits provided (i.e. short circuit between speaker terminals). Against accidental incorrect connections are no protective measures are effective. Incorrect connection as likelihood of rails and speaker outputs, or not detected electrical connection between the terminals also lead to damage to the components or total loss of the decoder."

Wow - you HAVE been warned!

I managed to fit the programmer in a Radio Shack 270-1802 project box, by removing the shell from a serial cable, and cutting an access hole for the track leads. I found a right angle power adapter (again from Radio Shack)


This should protect it from shorting against something




CT Elektronik programmer - software programs

The decoder is programmed with a series of *.wav files a template file for the sounds and a CV definition file.

There there is an array of programs available:


This is a dos program, it takes 3 parameters, the CV list file, the COM port on the PC, and the template file.



A windows program, which works with sound projects. Many people have trouble installing it. It apparently calls FILLFLASH to do the programming.



This program updates the firmware.



Preparing sound files:


If using Fillflash, the input to the software consists of a template file,  file specifies which and how many wav files will be used and a file of CV settings.


First you should start with a template file that is close to what you want, get one here: http://sounds.huebsch.at/Sound_Script/SoundList1.pl


Modify the template file to be what you want. I'll put a sample template file at the end of this section.


Also same goes for the CV settings file.


Next you want to get all the sound files that are specified in your template file. The files need to be in the same directory as where you run Fillflash from. The CV file is just a list of CV number and values.


I have found that the file names under XP had to be no longer than 8 characters (not counting the .wav extension)


If you are going to use the Soundprog program, you can build a sound project file from sound files (*.wav) , or load one and edit it.


You can edit wav files to customize them of course, here's a suggestion for a wav file editing software: http://www.nch.com.au/wavepad/


Note all sounds are in a 11025 hz sampling rate and in 8 bit unsigned format



Performing the sound programming:

First, hook up the programmer. Polarity to the decoder is important. Connect the red wire of the decoder to the red wire on the programmer. 

Make sure you have a speaker connected.

You need a com port that has all the signal lines connected, as the programmer apparently checks for flow control lines.


If programming is working, the power led will go out for about 8 seconds at first, and the screen says something about 10 seconds for reset.

As the programming starts, the speaker will beep regularly, and the programm LED will flash in sync with the beep (it's the LED by the large electrolytic capacitor)

The format for running Fillflash is: fillflash (note only com ports 1-4 are supported)

The sound file is normally a .txt file, the cv file is normally a .dat file, though I believe it does not matter.

There will be a message programming xxx of yyy, how many slots are to be programmed (xxx) out of the total slots (yyy) available.

At this time, I cannot get this to program, the beeping starts and continues up to about a count of 172 to 200, then the beeping and led flashing stop. The program terminates, but nothing changes in the decoder.




Firmware updates for CT Elektronik decoders:

Again, Arnold's Modell WEB to the rescue: http://amw.huebsch.at/TranFirmWare/Tran_Firmware.htm

Note: a good site to get the latest firmware updates is http://www.1001-digital.de/digital-hilfe.php go to the DCX75 page and translate with google translate.

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