RailCom is the name of the technology of bi-directional communication developed by Lenz according to the RP 9.3.1 and RP 9.3.2 of the NMRA.

RailCom allows an external device to be able to read real data transmitted from a decoder. These data can include among others: the actual speed of decoder, its load, the contents of any CV and its address.

To enable the bi-directional features of RailCom these components are needed:

1. A RailCom decoder that transmits the information (Lenz Gold, Lokpilot v3, Zimo MX64, LD-G-32, LD-G-33, FD-Rbasic,...)
2. A detector that can receive these transmissions like Lenz LRC120 or RailComDisplay
3. A cutout device that conditions the track signal for the transmission like Lenz LZV100/LV102 or NanoX-S88 command station.

For data transmission from the decoder to the detector is necessary to interrupt track power between DCC packets. This interruption is called 'cutout'. The transmission interval is divided in two portions, called channels. Each channel can be used independently for data transmission.

Bi-directional communication is enabled in the decoder with CV29, bit 3. Some decoders in the CV28 indicate the data messages transmitted. The usual configuration of this CV is:

CV28, Bit 0: Channel 1 used for address broadcast.
CV28, Bit 1: Channel 2 used for data (CV, velocidad, etc...)
CV28, Bit 2: Channel 1 used for command acknowledge

The usual value for CV28 is 3 (bit 0 and bit 1 active), then the decoder transmits its address and the aditional data

RailComDisplay

Local display of RailCom data

RailComDisplay is a local detector that displays data transmitted from RailCom decoders. When a locomotive enters in a isolated section connected to RailComDisplay, the data transmitted by the decoder will be displayed: its address and depending on decoder its speed, temperature and load.Neither does it matter whether the locomotive in this section stop or whether is in motion, data are send continuously

It also can display the CV value when they are read using PoM while the locomotive is in the isolated section

RailComDispay requires that a 'cutout' device conforms the DCC signal, to be able to visualize the transmissions and the decoder has active the RailCom functions. The isolated section should be at least twice the length of your longest locomotive.

Installing RailComDisplay is easy; signal from booster is connected to J and K terminals, and the isolated track section to the terminals J1 and K1. Data are displayed in a 16 characters, two lines LCD display. If you use backlight, connect to an external power supply, not to the internal 5V.

In order to program the PIC you can download the HEX file.

Download the manual, schematics and the PCB here in PDF format, if you want to build your own PCB or identify componets see this tutorials.