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Hardware Support: NAC Services RPS

Please note that JMRI's RPS support is being rapidly improved. This page refers to most recent JMRI test version. If you're using an RPS system, you should update to new test versions as they are announced.

The RPS System allows you to locate the exact position of locomotives and other rolling stock that have been equipped with transmitter decoders. The system makes up to 10 measurements per second and each reading is accurate to much better than an inch, which makes many imaginative uses possible.

Supported Hardware

DCC Systems

The RPS system works in conjunction which your DCC system to control when the RPS transmitters are activated. You therefore need a working connection between your DCC system and JMRI to use RPS.

At the present time, RPS is supported with DCC systems from:

Others may work, and we're interested in making them work, but they haven't been tested in combination with RPS yet.


First, get your DCC system working and connected to JMRI. As a good test of the connection, you should be able to turn your layout power on and off from the JMRI Power Control in the Tools menu.


Next set up the RPS hardware following the RPS instructions. You may want to only install a few (but a minimum of three) receivers while you're first getting the system working.

Next, connect your computer to the RPS using either a USB connection or an RS232 cable from a serial port. If you use an RS232 cable, note that it should be a "straight-through" or "modem" cable, not a "crossover" or "null-modem" cable.


RPS Connection pane

To configure RPS in JMRI:

At this point, your RPS system is ready to go.

To have your RPS system start measuring positions, you have to tell it to poll the Locomotives in which you've installed RPS transmitters.
To do this:

To see that the system is working, open the "Debugger Window" from the RPS menu. You should see time readings coming in and being converted to positions. You can also check the communications with the unit by opening the "RPS Monitor" from the RPS menu.



JMRI provides a number of tools in the RPS menu for working with an RPS system:

RPS Monitor
The pane displays all traffic seen on the connection
RPS Monitor Pane
Receiver Control
This is where you enter position information about your receiver positions, etc.
Receiver Control Pane
Polling Control
This is where you tell JMRI which locomotives have RPS transmitters, and how often you want JMRI to poll them.
Polling Control Pane Older Polling Control pane
Polling Control Pane v4.1.6 Version 4.1.6 Polling Control pane with new options
Debugger Window
This tool shows you the readings and measurements as the system makes them.
RPS Debugger Pane
Tracking Display
This tool shows the points as they are measured on a graphical display.
RPS Tracker Pane
Sound Speed Monitor
This tool lets you see and set the speed of sound used by the RPS system, and can set it automatically in certain cases.
Sound Control Pane
RPS Alignment
This tool lets you read and calculate spatial coordinates.
RPS Alignment Pane
You can also display RPS information on PanelPro Control Panels using an "RPS Icon".

RPS information may be used to detect occupancy using JMRI RPS Sensors.


Third Party info

More information on the RPS Web Site.