01/16/2026
Implementing signaling on modular layouts is a challenging prospect that real railroads do not know! The real world always stays in the same order!
The Free-mo community has adopted a clever architecture known as the Modular Signal System (MSS) to attempt to implement signaling. MSS is marvelously elegant in its simplicity. However, this simplicity also describes its functionality. When we talk about prototype signaling, MSS can only simulate simple single direction Automatic Block Signaling which was used in only very specific situations, definitely not single-track bidirectional lines. Even rulebook and timetables that listed a territory as ABS was often referring to Absolute Permissive Block (APB) signaling. Operations was never bothered to distinguish them since the rules were basically the same under both signal system types.
Signalogic Systems was asked to see if a method could be developed to implement a more realistic signaling system over MSS. A decade of trials lead to what we call Active-MSS. An implementation that can pass more realistic signal information over an MSS connection if another Active-MSS node is present at the other end, otherwise standard MSS is implemented. We have successfully implemented prototypical signaling using APB and Centralized Traffic Control (CTC) over Free-mo layouts. It should be noted that any modular/sectional layout can benefit from Active-MSS.
Our DBM signal controller will soon be openly available for modellers, and with it, implementations of Active-MSS!
