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DCC – Where trains will do as they are told!
Article kindly submitted by Model Train Club Member Roger W.
Despite DCC being around since as early as the late 1980’s, many model railroaders are still happy operating the older analog DC systems. From my limited 14 year experience in the hobby there still seems to be some confusion with how DCC works, especially among some of the veterans, and those ‘newbies’ who we desperately need to attract and encourage into model railroading.
Although the purists in the hobby might not approve of my following explanation of how DCC works, I’ve written it in very simple terms for everyone to understand. After all, for this hobby to continue successfully into the 21st Century, we need to encourage youngsters and ‘newbies’ into the hobby, without frightening them off with unnecessarily complicated terminology. When they get comfortable with the basics, they’ll hopefully progress to understanding the more intricate stuff. So here I go with my explanation of …
How DCC works
Basically every locomotive operating on the DCC controlled rails will have a small decoder fitted inside. The data commands will be transmitted to all locomotives at the same time. However each loco will have its own unique digital address, and when the digital signal is transmitted along the rails to a specific locomotive, only that loco will respond. The other locomotives on the layout will ignore any commands for the other loco, and continue operating in accordance with the last instructions that were sent specifically to them. So, if a loco had previously been told to “STOP”, or if the loco has not been given any instructions since turning on the DCC system, the loco will remain stopped.
It is a bit like when you have children – you assign each child a name, and they will (hopefully) respond when their name is called. However, unlike a child, a decoder will always do as it’s told.
So, a decoder will do “precisely as instructed”, immediately it receives specific commands… and, it will ignore commands sent along the same rails that are intended for other decoders.
DCC is not just for loco operation
DCC can be used for operating various devices and accessories (signals, sounds, lights, points, motors, etc), as well as for locomotive operation. Data will be sent to a specific decoder instructing it to act upon a command – be it turning on a light, starting an engine, or activating a whistle. Once the command has been given, the device will remain on that setting until it receives another unique command.
I gave the analogy earlier of decoders being compared to children; however instead of being given separate names, decoders are given separate address numbers to identify them. The advantage is that the operator can send different commands to each loco by calling up the address number of each loco, just like a parent would call out to each child by name.
Operating separate locomotives and accessories at the same time
Hence the great benefit of DCC – several locomotives can be operated on the same track, at the same time, just by calling up an address number and issuing specific digital commands. One loco might be told to move off, while another loco will remain stationary until it is instructed to do otherwise.
In practical term; a train can be set to operate on the main line, and then another locomotive (with a different decoder address) can be sent a signal instructing it to begin a shunting task on a siding. The train on the main line will continue operating uninterrupted whilst the other loco completes its tasks.
In another example; a loco could be stopped at a station platform and a second loco could be moved into position behind it (and even coupled to it) without the first loco moving, or needing an isolating track section. The two locomotives can even be coupled together to pull a heavy load by using a temporary address number. Both loco motors would be set to be controlled by that one temporary address number.
Depending on the system, there is generally an ‘ALL STOP’ button on the console or controller in case of an emergency. Activating this will stop everything, to allow for the problem to be fixed. Usually each loco is started again in turn.
In summary; several locomotives can operate at the same time thanks to DCC. The system can also be used to control train lighting, points, signals, and even ‘on-board’ effects like whistles, horns and chugging sounds. DCC provides more flexibility and control so increases the variety of possible functions on a model railroad.
Thanks Roger for taking the time to write this article and for allowing me to share it with the 10,000 weekly readers to this blog. Your contribution to the hobby is appreciated.
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7 Responses to DCC – Where trains will do as they are told!
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Well put Roger. I think that explains things nicely.
Too many people want to get technical (although they don’t always know what they are saying) and that only cofuses.
I quite often use the likeness to email (for the modern folk) we each have seperate addresses and the message has to be sent to the address concerned.
Cheers Derek.
You don’t have to worry about the kids do the electronic thing there already doing note pads, cell phones and other devices. The problem is to try to get them interested in trains.
The other problem is keeping the kids outside so they don’t disturb there grandmother or mother they get frustated when kids are in mom’s way.
Every new technology when it is introduced in a given environment, it takes some time to be fully understood by all and there is always a portion of people who do not accept it until some time later no other option, but to conform and start to use it, even if it still retains its taste for the old way of doing the thing.
Writers still use typewriters instead of computers, music enthusiasts, still maintain your vinyl record collection, even if they already have an equivalent collection of CDs and DVDs.
The same thing happens with the DCC. We are in the acceptance and Discovery phase, but no return. Soon the factories no longer make models without DCC.
Today we have the issue of cost, which is still high, but it has been much higher and decreases gradually, while innovations are being added.
J.Oscar
DCC is simply a way of making each device addressable in sort of the same way that our cable boxes have unique identifiers making them addressable. Model railroading is a great hobby. But it’s growth is hampered by the expensive nature of all the equipment required. A locomotive for the same price as an HDTV is absurd. All this stuff is now made in China and even when you figure in the costs of shipping to the US/UK/EU it’s way overpriced.
Roger. Your explanation of DCC was well put. But I would like to add that there can be no breaks in the track which includes points / switches. They have to be Electro frog, this allows the signal to be uninterrupted . This I found out too late and it became a costly fix. Keith
Pretty well sums up the advantages of DCC. I was content to watch the trains go round. Two different railroads intersecting two separate areas. My 18 year old says “lets DCC a section”. I now have two different railroads intersecting two separate areas, with DCC. The sounds and action are much closer to real railroading. He did the wiring I am enjoying the fruits of his work. When he comes home from college, we play trains together. Not sure if he would still be as interested if the trains just went round and round. The results, priceless.
Thank you, Roger! Very useful and easy to understand.