Hey Guys:

We have a DCC - JMRI with SPROG 3 system, with Kato Unitrack layout operated by a Windows 10 PC & cell phone throttles. There are no physical Command Station or throttles.
We are thinking of a stand-alone LocoNet for integrating LocoNet compatible accessories (we already have 4 DS64's & 2 BD4's working on the layout) & would like to know which products available with you would work with our existing system.
I understand that Digitrax PR4 and RR-CirKits LocoBuffer no more provide the "termination" needed. 
Would RR-CirKits SSB Gateway plus a LocoBuffer-USB do the job?  How would the RailSync lines provide the DCC information required by the Digitrax detector devices?
Thanks, Shailesh

Hi Shailesh:

Actually, if you are running trains with the SPROG3, the SPROG3 is acting as the command station and booster for the layout.

Both the SSB Gateway and LocoBuffer USB do essentially the same thing: both units allow you to interface a computer USB port to the LocoNet. The SSB Gateway does provide the required LocoNet termination, the LocoBuffer does not. Of course, the USB port must then be controlled by JMRI (or similar) software. The problem is that you must tell the JMRI software what device to use to control the layout. You will only be able to use either the SPROG3 or the LocoNet. Essentially, the USB port controlled by JMRI is the cab bus and either the SPROG3 or the LocoNet interface is the command station. You are only allowed one command station on a layout, and JMRI follows this rule.

You could have two separate computers running two instances of JMRI (I am not sure JMRI will let you run 2 instances on one computer), one controlling the SPROG3 and one controlling the LocoNet. There would be no cross control. The SPPROG3 would control train movement/control and the LocoNet would control accessories connected to LocoNet. This might be useful if you operate using a dispatcher.

The LocoBuffer is expecting to connect to an existing LocoNet, so the Railsync is provided by the command station, not by LocoBuffer. Thus, if you use the LocoBuffer, you will also need a Digitrax command station if you want the Railsync signal (see below). The SSB gateway DOES NOT provide Railsync signals. It simply provides DC power on the Railsync lines. In a Digitrax system, the command station provides the Railsync signal which is then rectified by LocoNet clients to provide operating power. The SSB Gateway simply provides DC power on the Railsync lines for client power, but there are no data provided.

If you want to use LocoNet to provide control/feedback of accessories while controlling the layout with SPROG3, you probably want to use the SSB Gateway as the LocoNet controller. I think you will need a separate instance (as mentioned above) of JMRI to control this LocoNet, and its commands and data will be separate from the SPROG3 control commands and data. Basically two independent control systems (which could be a dispatcher for one and engineer for the other).

If you want to control both LocoNet and train operation through the same device (i.e. all data are available to all units on the layout), then you will need to replace the SPROG3 with a Digitrax command station (the SPROG3 will still function nicely as a programming interface - its primary design function). In this case, you would use the LocoBuffer to interface the command station LocoNet to JMRI via the LocoBuffer USB port to your computer. My personal feeling is that this is the better choice of the two. Your opinion may vary!

Hope this helps you move forward.