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8 Pin or 21 Pin DCC Equipped?

Reg asks:

“Can someone tell me the difference in functions of 8 pin and 21 pin sockets? I’m trying to get my head around DCC and am not sure if all locos should operate with the same accessories? Would 21 pin be better?”

Have your suggestions published below.

5 Responses to 8 Pin or 21 Pin DCC Equipped?

  • Herveysays:

    It depends what you want to do. If all you want is your loco to move, have the headlight and rear light and up to 2 additional function then 8 pin is adequate. If you want all sorts of additional operating lights that would be individually controlled then you are going to have to go to 21 pin. To some extent the era you are trying to model may help answer your question. Modern era has a lot more “safety” lights and these re easier to emulate with 21 pin. If you are modelling steam or transition you can probably get away quite well with 8 pin.
    If you are new to DCC you should probably get comfortable with 8 pin before diving into 21 pin.

  • Nigelsays:

    There is an incredibly helpful information sheet via the following link which will tell you all you need to know and a lot more besides:


    Often, your choice is dictated by the locomotive itself with manufacturers tending to favour particular decoder configurations – in the UK for example, Hornby favours 8 pin with a few smaller locomotives taking 6 pin – other manufacturers favour 21 pin or one of the newer types, particularly where more lighting functions are required.

    If your locomotives are not DCC ready (i.e. have no decoder socket provided) then you’re probably going to find it a lot easier to go with a wired 8 pin socket with the red & black wires going to the locomotive pickups and the orange & grey wires going to the motor. It can sound daunting until you do it and I’ve successfully converted 50 year old locomotives from my childhood to run on DCC. You just need to make sure that decoders being fitted to older locomotives have a high enough current rating to cope with the more primitive motors.

    Good luck!

    • Thom Harrissays:

      Thank you for the invaluable handout!

  • Frank Bsays:

    I suggest getting a basic book on DCC to get a good overview of the subject. Then you can decide which functions you want to use. Simple decoders just do motor control and a light or two, more complex decoders offer sound and individual control over multiple functions.

    Many locos are available with full DCC already installed, or you can buy decoders and fit everything yourself if you are technically minded.

    Personally, I really love having the sound effects !

  • geoffsays:

    As others have said, generally more pins means more functions can be “operated” on the locomotive. That said, unless you are building the models yourself, you have to go with what the manufacturer of the model you want is providing. It would be nice if all the models had the same “size” of decoder, since then all your locomotives would have the same operating features. But often you have to go with what’s available for what you want to model.

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