CTS (Composite Transfer System) is a internal master/slave system relying on physical composite connections instead of radios which traditional master/slave systems use. CTS aims at creating a one setup system, although complex in nature, when broken down into its various parts. It is actually very straight forward. CTS as a whole features different parts (ranging from 1 to 4), here they are in brief detail listed below.

Part 1 - The main controller used in trains with CTS, here you will find all the logic for all the various functions. Any amendments (which is what the A stands for in 7A1) that are released may not be entirely stable and I recommend you stay with the current amendment number (A1 as of now) at the time you installed until the next revision is posted. Part 1 will act as a listening device for when it is not in charge (does not have the master signal) and will pass along CTS data to adjacent cars.

Part 2 - The logic for the audio connections, this will deal with the PA, part 2 controllers change their listening or transmitting modes depending on the location of the microphone ensuring every car with part 2 is receiving audio data. Please note this is completely outside the realm of radio which is entirely separate and should not be associated with part 2.

Part 3 - The logic for the video connections, you can hook any video connection up to part 3 and select it to be a sending or receiving controller while in operation meaning you can have a hive mind of inputs working together to feed info into 1 monitor for example. Or on the other hand cascade a video output across multiple trains, for example passenger information screens from one source.

Part 4 - This is a user created controller that is used for MU operation, by creating a controller that will feed inputs into one single composite output for the part 1 to spread across all the other trains. It will ensure all trains are in sync, not to mention all inputs are received with trains that are connected.

CTS started off with the class 334 v2 which featured a really primitive version of MU, eventually part 1 controllers emerged but as multiple micro controllers, this made it hard to share as it would add to the complexity of the build. By having one controller for each part, it means if the user chooses to update to a new revision assuming there is one. Then its as easy as pulling a build up, clicking on the microcontroller, updating the microcontroller and saving the new build.