What is Hornby TTS ?

In this article I will explain what many people seem to be asking – what is Hornby TTS ?

‘Twin Track Sound’ (TTS) is basically an 8 Pin decoder chip that has two sound channels which will enable specific sounds to be played at the same time, for example:-

  • Realistic Chuffing Sounds
  • Engine Revolutions
  • Whistles / Horns
  • Brakes
  • Wheel Slip

There are also additional sounds to this, and once I get a full list I will update this.

What is Hornby TTS

Hornby TTS is essentially a decoder chip that is designed to fit inside a TTS enabled locomotive.

What can’t the TTS decoder chip do?

TTS sound functions will only work when used on a DCC activated & controlled layout. However, it is important to note that unlike DCC operated layouts, a TTS decoder fitted locomotive will work on a standard DC controlled layout, the sound effects will NOT work. So, to reiterate, you will need a DCC controlled layout to experience TTS enabled locomotives.

As TTS decoders can play only up to two sound files at once, you will only be able to experience just one running sound (eg Chuffing); and one other sound (eg Whistles) at once.

Can I fit a TTS decoder chip into a loco I already own?

Yes. Hornby have released a whole range of TTS decoder chips designed for many classes of locomotives (Steam & Diesel / Electric). Please note though that all TTS decoders will require an 8-pin plug. A full list of the available TTS Decoders can be found here via the Hornby website.

If your locomotive has a 21-pin socket then an adapter can be purchased directly from Bachmann.


  • Will allow 2 simultaneous sounds to play
  • Will still work on DC operated layouts (but without sounds)
  • There are many decoders available to fit a whole range of locomotives


  • Sounds functions will only work on a DCC operated layout
  • Only the running sound and one other sound (eg whistle) can play at once


Just like DCC, the invention of the TTS decoder chip will further increase the enjoyment experienced for any railway modeller. There is nothing like experiencing the realistic sounds from a Hornby Steam or Diesel locomotive, and now that there is a massive range of compatible TTS decoder sockets, your older locomotive can now benefit from this amazing technology.

1 thought on “What is Hornby TTS ?”

  1. Hi Tim, thank you for the detailed review. I believe you have covered the fundamentals of the TTS decoder chip, and please do update us if there is an update on these gadgets. I also appreciate the clarity especially on the aspect of the function of the TTS decoder chip in which you clearly stated that the TTS only plays the Chuffing sound and the whistle at the same time, this is clear and straight forward as it explains why it is called the twin track sound. Thanks again on the simple and straight foward information.


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