BAS Rail & Electrical Pty Ltd

XPT Speed Signal Converter Module (SSCM)

The purpose of the XPT Speed Signal Interface Module (SSCM) is, by using the existing 3-phase signal from the Hasler axle generator, to detect current speed and translate it into a pulse train with a frequency proportional to the speed, which is then used by the Vigilance Control Unit to enable it to perform its speed-based functions.

Furthermore, the SSCM also has a 3-digit LED display, showing the current speed. This can be used to verify that the unit is working properly.

The pulse train output to the vigilance control unit is galvanically isolated from the rest of the circuit.

The speed conversion and all other tasks are performed by a PIC microcontroller.

To be able to test the SSCM, a dedicated test device was built, which generates a 3-phase signal with similar level and frequency as the Hasler axle generator. Thus, the unit can easily be tested off the train.

A total of 22 units were built and delivered to RailCorp in 2005.