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MSS User Guide
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Modular Signal System - MSS
The MSS User Guide is intended to educate model railroaders about how the Modular Signal System works, why it is designed as it is, and the best practices to follow when implementing the MSS in a module or layout.

This User Guide is a living set of documents that will continue to evolve and improve as MSS users ask questions and provide feedback. If the MSS User Guide doesn't answer your question, or you find something confusing or incorrect, feel free to contact the author and MSS co-inventor Gregg Fuhriman at I'll update the User Guide accordingly.
Modular Signal System
User Guide - Part 1
Part 1 is a must-read for every MSS user, explaining the inner workings of the overall system and interactions of the three MSS Layers - Occupancy Bus, Detection, and Signaling. Revealed here are the functions and operation of the eight MSS Occupancy Bus wires, the purpose of the combined current and optical detection scheme, and the requirements of signal logic circuitry. Updated 12/19/15.
Modular Signal System
User Guide - Part 2
Part 2 is all about planning and designing an MSS system into your module or layout. How to make a list of items needed, how to select MSS hardware, how to prepare for installation of track, wiring, and signaling equipment, and so forth. Updated 12/24/15.