DCC Locomotive and Train Addresses
The DCC standards (specifically Recommended Practice 9.2.1, PDF) allow for two kinds of addresses to be used with mobile decoders used on trains: short (7 bit) and long (14-bit). The short form allows for addresses 1 to 127 (some systems limit this to 99) and the extended allow for addresses from 127 to 9999 (technically there are enough bits for a few thousand more addresses, but 9999 is the limit in practice). These are sometimes called “two digit” and “four digit” addresses, although the “two digit” ones can be up to 127 with some command systems.
Addresses to Avoid
Because some command stations disallow use of addresses 100 - 127, these should be avoided. Further, as consisting uses addresses 1 - 127 in a manner than conflicts with trains addressed using these, the remainder of the range (1 - 99) should be reserved for consisting if you plan to use it. I may, so I won’t number any trains below 128.
From this it follows that all of my trains will be addressed with four-digit (also called “extended”) addresses.
There’s a further issue since I use Digitrax. For some reason they chose to limit the maximum address to 9983, so I can’t use the last sixteen addresses. That leaves me with a total of 9,856 addresses I can use, and even at my rate of acquisition it should be several centuries before I run out. Somehow I don’t expect that to be a problem. In fact, I’m going to deliberately make my addressing plan “sparse” to allow room for future enhancements to DCC (see the Addressing section below).
Trains with Multiple Decoders
A typical DMU/EMU (diesel or electric multiple-unit) model will need three decoders: one in the motor car, and one in each cab car to control the directional head/tail lights. These could be given separate addresses, and then consisted, but doing so would be wasteful of addresses and limited by the small number of consist addresses. Thus, all three decoders of a train will be given the same address. One implication of this is that I shouldn’t use Operations Mode (on the track) programming, unless I want to reprogram all three. As I plan to do decoder set up using a dedicated test track and my old Zephyr command station, and JMRI software, this won’t be a problem.
Sound decoders would normally also be motor decoders. However with EMUs, it’s possible I may end up with sound installed in a separate car from the motor for space reasons. If this happens, my intent is to use the same address as the motor decoder, so the two will be synchronized.
There is one use for separate addresses, and that is in sets with two motor cars, as discussed below.
Consisting is used when two (or more) normally-independent locomotives are going to “double head” a train, and you want one throttle to control both equally. For this to work, the two should be of similar design, and speed tables used to “speed match” them, so that a given throttle setting makes both operate at the same speed. Otherwise, one will always be pushing/pulling the other. While normally this is applied to locomotives, there’s a use for it with multiple-unit trains as well.
Some of my EMU models reflect 10+5 sets (or similar arrangements) where two trains are combined into one as they approach a city center. For most of these, there is only one motor car, and I only need cab decoders in the two outermost cabs, as there is no reason to separate the two sets. In some, however, there is a motor car in each set. To allow these to be operated independently, I will number each set uniquely, and consist them when they are operating together.
I could just assign addresses sequentially. However, I’m going to divide my 9,856 addresses into subranges to organize things a bit.
- 1 - 99 Consists
- 100 - 127 unused
- 128 - 999 for non-prototype equipment (e.g., track cleaners, etc) and other mobile decoders not using a train address
- 1000 - 1999 Locomotives (both freight and passenger)
- 2000 - x Commuter and Suburban EMU/DMU Trains
- 6000 - y Limited Express & Joyful Trains
- 7000 - z Shinkansen
- 8000 - a Subway Trains & Trams
I haven’t figured out what X, Y, Z and A are yet. I’ll start from the low end of these ranges, and may subdivide them later.
Further, I won’t number trains sequentially, but will only use every tenth address (e.g., 1000, 1010, 1020, etc). This will allow for later addition of subordinate decoders (e.g., to control couplers, automatic doors, restaurant-car table lights, or whatever may come) if something is needed that can’t use the basic train address. As presently laid out, this allows for 400 commuter trains, and 200 of each other type, which should be more than enough.
The following addresses are assigned:
1010 - Kato DE10 1188 (Warm Region)
2010 - Kato Chūō E233
Limited Express & Joyful Trains
6010 - Kato E655 Nagomi
Subway Trains & Trams