• Modular Signal System Crossover Module

Modular Signal System Crossover Module




This product has been discontinued.  When existing stock is depleted, we will not build any more except by special arrangement.

The MSS-CROSSOVER is a fully integrated and ready-to-use "crossover" node - block detection for a module without signals - for the Modular Signal System.   It integrates a highly-reliable current-based DCC block detector, an auxiliary occupancy input to use with turnout position or other inputs, a rugged and reliable MSS bus interface, and plug-and-play RJ45 connections.  Works with a wide variety of power sources including Free-mo's accessory power bus.  Simply connect power, run one leg of track power through the current sense transformer, plug the MSS bus in both ends, and your module is ready to participate in an MSS-signalled setup!


  • Completely integrated - no additional detectors required
  • Fully compliant with the Modular Signal System 2.0.1 standard
  • Easy installation with connectors and terminal blocks
  • One current-based DCC block detector with adjustable sensitivity
  • Isolated detection to prevent coupling track power and signal systems
  • Auxiliary occupancy input - show “occupancy” in response to open siding switches
  • Rugged and reliable MSS bus drivers
  • Plug-and-play RJ45 connections
  • Powered from 8V to 20V AC or DC accessory power


2.5"(L) x 1.9"(W)

Many thanks to Gregg Fuhriman and other contributors for the development and release of the Modular Signal System specification.


The complete gEDA design files are available on GitHub.

User Manual


  • $25.00

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News & Application Notes

Introducing Modular Signal System Components

You may have heard about the Modular Signal System – it’s been slowly gaining support in the Free-mo modular community for about a decade now.  If you haven’t, read on – it’s an exciting new (well, somewhat new) option to bring ABS signalling and more to your model railroad.

The initial Modular Signal System (MSS for short) proposal was put forth by Gregg Fuhriman in the February 2005 issue of RailModel Journal.  He’d developed the idea along with others to bring simple signalling capabilites to Free-mo modular meets.  Traditional solutions, using pieces such as C/MRI or Loconet-based systems, are impossibly cumbersome to deal with in an infinitely-reconfigurable modular setup with participants coming from all over.  What was needed was an acceptably realistic signalling system that was plug-and-play – no reconfiguration required for the myriad of ways their modules could be put together at each meet.



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