2000: Gregg Fuhriman (Northern California Free-mo, aka NorCalF) installs commercial signal animator products on
his Glen Frazer passing siding Free-mo module. Optical sensors are used to set the signals to Stop when a train
arrives, and timer circuits sequence the signals to Approach and then Clear a short time after a train departs.

2001: Chris Palomarez and Michael Mosher (San Luis Obispo Free-mo, aka SLO-Mo) propose the concept of a
train detector wired to signals facing outward at the ends of a signal block, for use in Free-mo modular layouts.

2001-2004: Gregg Fuhriman expands the concept into a complete, multi-indication signaling system by inventing
the MSS core concepts of a modular Occupancy Bus Layer with Cascade and Crossover elements using Cat-5
network cables, a Detection Layer with complementary current and optical sensors, and a Signaling Layer. The
system is incorporated into NorCalF and SLO-Mo modules for testing.

2004: Gregg Fuhriman produces the Occupancy Bus Utility Board (OBUB) to help simplify the installation of
MSS into modules and layouts. The OBUB is the first product specific to the MSS.

2005: Rail Model Journal magazine publishes Gregg Fuhriman's article presenting the MSS to the model
railroading world. Later, this article becomes the de facto "MSS V1.0" standard.

2005-2011: The MSS grows in popularity among Free-mo groups throughout the US and Canada.
The 2011 National Train Show held in Sacramento, CA hosts a large multi-group Free-mo layout
featuring a fully operational MSS extending through most of the layout.

2011-2014: Barry Draper (Southern California Free-mo) invents the Approach Diverging feature used at
MSS junctions. Additional MSS-specific products begin to appear, many of which re-assign one or more MSS
Occupancy Bus wires for other purposes. Potential incompatibilities arise, leading to the need for standardization.

2014-2015: An MSS Standards development group, consisting of product manufacturers, produces the
MSS V2.0 Standard that specifies the MSS core requirements, resolves nascent incompatibilities, and
formalizes the optional Approach Diverging feature.

2015: The MSS V2.0 Standard is published on this website.

2015-Present: MSS V2.0 compliant products appear. The MSS user base continues to grow,
especially in the modular model railroad format.
Modular Signal System - MSS