I was thinking of putting this in the mfx-thread, but I did not want to derail it. So here goes:

I do not really have a problem with mfx or any other protocol for that matter. What I have a problem with is that all manufacturers seem to be unable to agree on which plug to use and how to implement it. It is nice that we have some standard plugs, but what good are standards when they are not followed.

Currently (in H0 and N) we have:
- NEM 651 (6-pin)
- NEM 652 (8-pin)
- NEM 658 (PluX 12, 16, 22)
- NEM 660 (21-pin MTC)
- NEM 662 (Next18)

There is plenty of room for whatever demands you may have. The PluX alone lets you do pretty much everything, was it ever that simple:

...because then we have:
- 21-pin (with amplified outputs, not really a known standard)
- Roco BR 110 Plux (with no taillight control, because it uses a NEM 652 layout on a Plux board - WTF?)
- MTC 14 (the all new Trix standard. What was wrong with Next18?)

This is crazy! Yes, there is some history to it, I can understand that, but not following the NEM standards is just wrong.

An example:
My Trix TRAXX has a so-called 21 pin plug, but for reasons unknown it does not follow NEM 660 (21 MTC). Trix placed the taillight controls on AUX 3 and AUX 4, which means that the AUX 3 and AUX 4 needs to be amplified for the lights to function properly. This is not part of the standard. Nice! (Need I to say that AUX 1 and AUX 2 are left unused?)

I would like to use ABC brakes on my locomotives. It is a nice and very well working automatic braking system. It is extremely easy to setup, and can be helpfull in all sorts of scenarios (it can also be an automatic breaking system if you implement it wrong ).

The problem is:

- I cannot use a Lenz Silver+, even though that one does not follow NEM 660 and have amplified outputs, but unfortunately no AUX 4. Supports HP1, HP2 and shunting (F3) lets you pass a red signal.
- I could use a Zimo 21-pin decoder, but then I would have to learn the inner workings of that one. The majority of my decoders are ESU LokPilots. Does not support HP2, but shunting (F3) lets you pass a red signal.
- I cannot use the LokPilot, because it does not have amplified outputs on AUX 3 and 4. It supports ABC though. Both normal speed (HP1) and reduced speed (HP2), does not support shunting past a red signal)
- I cannot use mLD, because it does not support the ABC-system. It will work with the light functions though.

I just wish I was able to buy a decoder from ONE manufacturer, so I could become good at tuning that decoder and know it inside out. Every time I need to take in a decoder from a new manufacturer, I need to learn the inner workings of that decoder. And that is annoying.

The solutions:
- ESU could make it possible to enable amplified outputs on the LokPilot 21-pin.
- Lenz could add AUX 4 to their decoders
- Trix could stop producing locotives which rely on non-existing standards (I think they have though, but that does not help my TRAXX'es).
- Märklin could enable ABC in their decoder (the CV's are there, but not responding to commands). It may happen if the hardware is there too, who knows.
- I could go all Zimo, but then I would miss the HP2 feature.
- I could re-solder the Trix board to follow NEM 660, effectively killing of the option to ever use AUX 3 and AUX 4. But that is really not an option - although at the moment - it seems to be the only one.

If the Trix board had followed NEM 660 to begin with - I would have complete freedom to choose a decoder of my liking - and all would be good.

Actually, the Zimo decoder is the same decoder hardware regardless if a customer chooses C-type or D-type. At least from MX634, using CV 8, it is possible to change the behaviour of the outputs. This can come in handy if someone accidentally buys the wrong decoder-type.

CV #8 = “3”  Change MX634D into MX634C
CV #8 = “4”  Change MX634C into MX634D

Nice feature. Unfortunately, the decoder does not support HP2 with ABC. I might need to live with that, unless I re-arrange the Trix board.

The story of the BR 103 really, really sucks, because it alienates potential 2-rail customers. They will look at it and think "I kind of expected something to be weird" and then they will go away and never look back. Customer lost forever.

There are at least three sockets with 21 poles: PluX22 (NEM 658), 21MTC (NEM 660), 21MTC (NMRA)

PluX22 seems to be a complete standard. IMHO PluX is a good choice for H0 locomotives.

Why?
Fleischmann do have 6 pole for H0 scale locomotivs,when there is hard of placement for the sound decoder and the speaker.
Of course do Fleischmann have 8 pole too,for smoke generator and telex coupler.
Depends if there is place for the PCB card with schnittstelle.
The more difficult locomotiv,the harder placement.