So what’s an OpSw?

The other day I got an email from a reader asking about how to resolve the “FF” warning on his Digitrax system. This warning tells you that the address memory in the command station is full and therefore you can’t select a new address until you make room. The process is pretty easy once you figure it out and it requires something called OpSw settings. So let’s first go over the process of making a change and then take a look at some useful ones. First and foremost, unless you are working with a DCS50 or 51, you need a DT400, DT402, or DT500 throttle to make these changes. You can also do it more easily using DecoderPro.

With DecoderPro go to the Loconet option on the horizontal menu list at the top of the DecoderPro window. Scan down the dropdown list to the setup command station option and click it. The window pane that opens will give you a list of the OpSw settings for your commamd station. All you need do is click on the “t” or “c” setting to activate or deactivate the specific OpSw. You can click the read and write buttons to read the settings and write them to the command station.

With a DT400, DT402, or DT500 throttle the process is a little more complex. First disconnect the command station from the Loconet. Plug the throttle into the command station and move the mode toggle on the front of the unit from the Run to the Op position. Next press the “SWCH” button and enter the number of the OpSw setting you wish to edit–the display will indicate either “t” or “c”. To change the setting press either the “t” or “c” button on throttle keyboard. To edit other OpSw settings continue by entering a different switch number. Once you are done simply set the mode switch back to the run position.

So which OpSw settings are worth considering? OpSw 15 will set a decoder to speed step “0” when it is purged. This can prevent unexpected runaways later. As I mentioned in my recent post OpSw 18 will extend the short circuit response time from 1/8 to 1/2 second and give circuit breakers more time to act. OpSw 20 disables the ability to operate analog locos using “0” bit stretching, something that can slow Loconet response times. OpSw 33 and 34 allow the unit to power up in its prior state and to allow power on at startup. Without this you must turn track power on using your throttle.

Four big ones are OpSw 36, 37, 38, and 39. OpSw 36 clears mobile decoder info and consists. OpSw 37 clears all routes, and OpSw 38 clears the loco roster. Finally OpSw 39 will clear everything in memory. Periodically clearing out some or all of these will allow the system to run faster and prevent the memory slots from filling. Clearing out universal consists may not be desirable if you have spent a lot of time creating them, however on club layouts this can be a necessary and convenient part of system maintenance. At my old club we did it once a month. It also is a good reason for using advanced consists instead of universal consists since their info is not stored in the command station.

One word of caution. Every Digitrax manual has a listing of these OpSw settings and what they do. Note that some say reserved or do not change–follow this instruction, don’t mess with these! Also make sure to use the OpSw list for your specific type of command station. Don’t assume they are all the same–most are but check to make sure! And when all else fails read the manual.


  • Thanks Larry, Your post was very informative. One additional piece of advise for your readers is to write down the OpSw settings as changes are made. I found it is very easy to loose place of what settings were changed.

    • Bob—that’s a very good point, especially if you don’t use DecoderPro. I make a note next to each one i the OpSw table found in the manual that comes with each DCC system. It also is a good idea to keep a notebook listing the exact type of decoder that you install in each locomotive. With some of these it can be a pain to get to them once installed and even DecoderPro may not be able to tell you the exact type.

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