Already familiar with the standard 6-Pin DCC plug, our friend “NEM 651” ? Meet Next18, Plux12 and MTC14; slowly making their way in our N-Scale locomotives.

I just bought a Piko diesel railcar with a Plux12, so I thought an overview of all these DCC plug types would be interesting. Oh, and also, it was high time to speak out: stop coming up with new plug types!

Foreword: It’s a small – now overcrowded – world

It”s no secret: new generations aren’t particularly into model trains. That said, European manufacturers have done a decent job recently, changing the hobby into something more future-proof. We have color touchscreens, iPad or iPhone apps, and more gadgets are coming….

As for getting a new clientele, Märklin has reportedly had a huge success with its “My World” toy range, and other brands offer “low cost” children proof H0 models. In a word: some of these manufacturers have understood the basics:

  1. The market is limited already: cherish & exploit the current base.
  2. The market is not getting any bigger on the long term: get young people to like trains, and fast!

Sadly, this time, those same manufacturers are shooting themselves in the foot. Simply said, the multiplication of DCC plug types – especially for our beloved N scale – is stupid :

  • It complicates the life of customers (Which plug is it? Which decoder fits?)
  • It complicates the job of DCC manufacturers (Release new decoders or abandon parts of the market).
  • It doesn’t make the customer stick to your brand.
    A DCC plug that is incompatible with my existing decoders could drive me AWAY from a manufacturer, but can’t make me stick to one brand. This is not the computing industry: customers will always buy trains from several brands, because each model is different.
  • It scares the hell out of people interested in model railroading, or a conversion from analog to DCC

It should be noted that the manufacturers have no excuse: it IS a small world. Many of them are located in Germany and meet regularly. In fact, 2 of these 3 news formats are already NEM “norms”.

If model railroading was a billion dollars industry, they could afford a war (think about Blu-Ray vs. HD-DVD, or VHS vs. Betamax); but it just isn’t.

So here is a short presentation of what you – the victim of this ridiculous format war – will have to deal with.

NEM 651 – The old lady

NEM 651 doesn’t require many explanations. It is the most common plug found in DCC ready trains, both in Europe and the US.
It is simple mechanically (6x 1,27mm Pins) and electrically. It supports a motor (of course), and two lights (front and rear), that’s it.

Kato Digital Plug – The exotic

Although Kato does provide European or US models with a standard NEM 651 plug (e.g.: 2nd gen Thalys), they have developped a digital plug of their own. It can be found for example in recent Shinkansen products.
It doesn’t do more than the NEM 651, in fact, it does less: with only 4 pins (motor and track), it is designed to be put in the middle of an EMU, therefore not controlling lights at all.

Plux12 – Same recipe, but better

Zimo - MX623P12 Dcc Plux12 Decoder

Plux12 Decoder (Zimo – MX623P12)

Plux12 is simple: it has 12 Pins (2 rows, 6 pin @1.27mm), which is basically a double NEM 651 plug. To be more exact, it has 11 pins (1 empty pin used to mark plug polarity).
Plux12 is not alone, the norm defines Plux8, Plux12, Plux16 and Plux22. However, the 12 Pin variant is what seems to be making it to our N rolling stock for now.

It includes 2 extra function outputs (i.e. 4 in total including front and rear lights), and 2 loudspeaker connections, which seems reasonable for what we can pack in our locomotives.
The NEM documentation also clearly states the necessary space to be reserved for the decoder. Something which – if respected – would save a lot of headaches.

Piko GTW2/6 - Analog board and Plux-12 plug

Piko GTW2/6 – Analog board and Plux-12 plug

Next18 – So fancy, but not flexible

Next18 (aka NEM 662) is “kinda like Plux12, but cooler”. It boasts a different connector, more compact, such as one seen on modern circuit boards.

It also has more functions:

  • 4 functions load outputs (front/rear lights + 2 others)
  • 4 logical functions OR 2 logical functions and 2 speaker outputs.

Now, technically, Next18 seems to be the most advanced plug.
But this norm has 2 flaws if you ask me:

  1. It has a split personality. The norm defines “Next18” and “Next18-S” (S as in sounds). These are actually similar plugs, but the “official” space to be reserved for the sound version is larger.
  2. Since the specific plug of Next18 doesn’t allow for any margin (the decoder needs to be flat, you can’t “gently bend” the pins as we are used to), that means a locomotive built for Next18 without sound will likely never be easily fitted with an Next18-S (sound) decoder.

Also, don’t get fooled by the fancy name. Because the connectors are so small, several pins are actually paired together (e.g. track pins), to allow for more power to go through. So in reality, there are not 18 pins on this decoder, only 14 ! (See specification PDF at the bottom).

Place for Next18 interface

Adding a Next18 adapter to all old locomotive

MTC14 – The unwanted child

MTC14 was announced last year by Märklin for the Minitrix N scale (see news in German here).

I have read different reports as to what it can do. It has 14 pins, can support 2 extra light functions, and also integrates 2 SUSI pins (i.e. external sound modules).

The fact is: this is a manufacturer-specific plug type. Märklin somehow disagreed with the others, and launched a new plug type on their own.
ESU or other decoder manufacturers have not – to my knowledge – announced any kind of support for MTC14; so if you buy an MTC14 locomotive from Minitrix, you’re pretty much stuck with buying the (only & overpriced) Minitrix MTC14 decoder.

Minitrix 12102, BR185.6 with MTC14 connector ©Minitrix

Conclusion and summary table

The “old” NEM 651 plug needs an upgrade, no one can deny that. We can pack more functions in N locomotives now than 15 years ago. The problem is not the NEM 651 being replaced, it is the plug standard becoming fragmented.

If NEM 651 were to disappear, my bet is on Plux12. It brings enough functions, has a clearly defined norm, and still uses “basic” 1.27mm connectors.
Next18 sounds fancy, but the plug doesn’t bring the flexibility needed in very small locomotives. Most of us have already played with (and broken), some of those NEM651 pins. It’s annoying when it happens, but at least we were given a chance to make it fit!
July 2014 Update: After testing, the Next18 interface now has my preference. Read the Next18 review here: Next18 digital interface: N scale’s future?

January 2015 Update:
Next18 (NEM 662) seems to be gaining traction, but all manufacturers don’t agree yet:
1) Arnold (Hornby International) is starting to equip some models with Next18, seems they have chosen their side (table in article updated).
2) Brawa announces further models with Next18 (news in German here). Doehler & Haass decoders are used for the sound models (which is new for Brawa).
3) According to some rumors, Piko may soon be using Plux16 (not Plux12) on some models. It’s the same interface with additional outpus/pins. Yet another annoying change from Piko (although to be fair, a Plux12 decoder will fit in a Plux16, but you may miss some train functions).
4) The (only) mTc14 decoder from Minitrix (66840) is actually a Doehler & Haass decoder (codename DH14), but there are already 3 versions on the market. People with a D&H programming device can detect the exact version they have and even benefit from the firmware updates from D&H (details in German on the D&H FAQ page).

Here is a quick summary:

StandardSupported byContacts
(Physical / Actually available)
NEM 651Nearly all N manufacturers6 / 6* 2 functions (Front/Rear lights)
Kato PlugKato4 / 40Models specifically designed for US / EU markets now include a standard NEM 651 plug.
This decoder only controls a motor, no lights.
NEM 658
Piko, Tillig...11 / 11* 4 functions (front/rear lights+2)
* 2 loudspeaker pins
1 pin is left empty (to determine plug orientation), hence 11 contacts instead of 12.
NEM 662
Arnold, Liliput, Brawa, Bemo....18 / 14* 4 functions (front/rear lights+2)
* 4 logical functions (low power, incl. 2 as opt. loudspeaker pins)
Some pins paired, hence fewer actually available contacts.
MTC14Minitrix (=Märklin)14 / ?* 3 or 4 functions (to be confirmed)
* 2 extra pins for SUSI
(ext. sound decoder)

Share your thoughts about all these plugs in the comments!

External links

Note 1: If you wonder why those are not available in English, ask the European MOROP in charge of publishing NEM norms… somehow there must be a guy in there still persuaded that French is an international language 😉

Note 2: To my knowledge, none of these plugs (except the old NEM 651) have been adopted or even reviewed by the American NMRA. I wish good luck to my American friends buying European rolling stock in the next months, finding appropriate decoders is gonna be tough!

This article was written with the N scale in mind
Although some of the content is relevant for other model railroading scales, if you are using another scale, additional or more accurate information might be available elsewhere!