Monthly Update: July 2025

July update. Work has continued on preparing the simulator software for timetable-driven trains with full block bells for August. Progress is slow as the author prepares to move back to the UK from two years on contract in Geneva. However, continue reading for an exciting hardware announcement…

Despite being planned for sometime, design work has finally started on a new Universal Signalling Interface (USI). This DIN rail mountable module will feature 8 channels of logic, which run into pluggable adapter boards to interface to anything up to 60 volts with bipolar supplies. Each input leg can read bipolar voltages too, between 1 and 60 volts, and both the inputs and outputs are optoisolated to protect any connected equipment. The adapter boards are designed to be cheap and replaceable, and normally feature a set of solid-state relays and screw terminals, although this can be further customised, for example to include electromechanical relays and pluggable connectors. Each channel will feature back-emf protection from coils using TVS diodes, which should preserve the fast response for bells. It is envisaged that the USI will replace the existing bell interface, but will run very similar firmware. The firmware running on the module supports interfacing to modbus over serial or TCP via wifi connection, MQTT via wifi, and direct module to module comms via wifi to allow block instruments to be connected together over the internet easily. We are also planning a compact interface for the latter, with a configurable power supply built in (the USI requires you to provide the various power supplies needed for your instruments, bells and other items).

Further details for the USI will be published later this year, but we should get some prototypes tested with a variety of block instruments before the autumn.