SA-DEC-4-DC & S-DEC-4-DC from LDT (Littfinski): 2 sturdy accessory decoders used under the biggest model train layout in the world!

LDT (Littfinski DatenTechnik)

LDT is a (medium-sized?) manufacturer based in Germany, though their website is available in a few languages. They have a large range of DCC (and Motorola) products for digital model trains.

I suspect not so many people have heard of LDT (I hadn’t until I started shopping for trains in Germany). Why do I have those modules, and why are they worth mentioning here? Two reasons:

  • The decoders are available (at least) EU wide. They are indeed sold by the German chain store Conrad Electronics, that I often mention here. This means the decoders are available through the national Conrad websites (,,…) and through the global
  • LDT products are used under many large layouts. Including the largest & awesomest model train layout in the world: the Minatur Wunderland in Hamburg. LDT describes in details which models are used in Hamburg on this page. That sure speaks well for the reliability of the LDT modules.

Specs & pictures

The SA-DEC-4-DC & S-DEC-4-DC are two completely separate devices. They look alike, and it made sense to review them together since they share a very common purpose under our layouts:

  • SA-DEC-4-DC – DCC 4x Relay decoder (German: Schaltdecoder)
    4 independently operated bi-stable relays  (for any item that needs constant power, e.g. lighting).
LDT SA-DEC-4-DC relay DCC decoder (electronic board)

LDT SA-DEC-4-DC (electronic board)

LDT SA-DEC-4-DC relay DCC decoder

LDT SA-DEC-4-DC relay DCC decoder

LDT SA-DEC-4-DC relay DCC decoder

LDT SA-DEC-4-DC relay DCC decoder

LDT SA-DEC-4-DC relay DCC decoder

LDT SA-DEC-4-DC relay DCC decoder

  • S-DEC-4-DC – DCC 4x Switch decoder (German: Magnetartikeldecoder)
    For 4 double-coil switches (for standard N-Scale switches with coils and 3 wires).
LDT S-DEC-4-DC switch DCC decoder (electronic board)

LDT S-DEC-4-DC (electronic board)

LDT S-DEC-4-DC switch DCC decoder

LDT S-DEC-4-DC switch DCC decoder

LDT S-DEC-4-DC switch DCC decoder

LDT S-DEC-4-DC switch DCC decoder

Ready to use or DIY kits

Before having a look at the SA-DEC-4-DC & S-DEC-4-DC decoders, a few words about the LDT philosophy.

Most modules are available in 3 versions:

  • DIY Kit – read to be soldered with the board and all needed components
  • Ready to use board
  • Ready to use board with plastic housing.

Obviously, the DIY kits are cheaper. Since the components are normal-sized, anyone with a bit of soldering experience should be able to build the modules successfully (20-30 minutes).

Conrad seems to only sell the first 2 versions, but you can buy the separate plastic housing if you want to:

  • SA-DEC-4-DC – DCC 4x Relay decoder
    DIY Kit:  Conrad no. 212172
    Finished board: Conrad no. 212180
  • S-DEC-4-DC – DCC 4x Switch decoder
    DIY Kit: Conrad no. 212113
    Finished board: Conrad no. 212121
  • Plastic case LDT-01 for both models: Conrad no. 240015
LDT optional electronic board case

LDT optional electronic board case


Those modules are, by design, extremely simple. There are no CVs, no complicated settings. For both decoders, programming is done the old fashioned way, in a few seconds.
Just press the programming button, send an order from your command station, the module then takes the corresponding address and the 3 following (e.g. send 1, modules gets addresses 1 to 4).

Tests and impressions

The switch decoder works well with classic points (in my case, Fleischmann N).
Unfortunately, the relays on the relay decoder are a bit noisy. This is not unusual, since relays are actual mechanical devices. I use these to switch some layout lights on and off.

I have had those modules under different versions of my layout for more than 4 years. Some I had bought as DIY kits, others as ready to use modules. Those modules have always worked completely reliably, although my layout isn’t as intensively used as the Hamburg Wunderland !


The LDT switch and relay modules are single-purpose no fuss devices. They do little, but they do it very well. Programming couldn’t be easier, and if you can solder, the DIY kits will save you a bit of money (e.g. as of July 2014, the switch decoder for 4 switches costs about €21)Beginners can get the ready to use devices.

My personal choices have evolved. Because my layout is always evolving, I now prefer to buy universal modules. Those can be reprogrammed for any purpose (switches, lights, signals). The drawback is they are more complicated, and sometimes more expensive. I recently reviewed the advanced Qdecoder Z2-8+ which is now one of my favorites.
Despite this change of heart, LDT modules still operate many essential parts of my layout. I would still recommend them to people looking for simple & reliable DCC devices.

External links

I always try to be fair and square when giving grades, see the details about the evaluation criteria here !

Reminder: I am a hobbyist and these articles only represent my personal views. I am not receiving any compensation, in any form, from the brands or stores mentioned here. The product names, marketing names, and brands mentioned here are the property of their respective owners.