Simply put – Repoint is a fault-tolerant switch
Fault tolerant switch
Other switching solutions use a single motor to move the switch rails. If it fails, there is no back-up. For passengers, this means delays and cancellations whilst a maintenance team rushes to undertake an emergency repair. Repoint uses architecture similar to aircraft flight control systems with multiple channels for actuation, locking and detection. If a fault occurs in a single channel, the switch continues to operate – without the need for immediate repair – and services can continue to run as timetabled.
Unlike other switching solutions, locking is provided passively by the position of the rails. The actuators lift the rails out of their lock to move them. Any single actuator is capable of providing this motion and, in the event of an actuator failure, the switch is still locked in place throughout its length.
Currently, switch maintenance is line-side, and the line is closed to traffic whilst the switch is inspected and adjusted. Maintenance of Repoint is via LRU’s (line-replaceable units). The LRUs are standardised, sealed, and maintenance-free for their operational lifetime. At end of life, they can be replaced in a matter of minutes, and returned to base for overhaul in a cleaner, safer environment.
The demonstrator switch we see today has the Repoint multiple redundant actuation mechanism applied to a conventional switch layout, however, during its early project phases, the Repoint concept included a stub switch layout. Although this was considered too big a step to take to full scale demonstration for the scope of the current project phase, the project team believe that the stub switch layout has additional benefits and intend to pursue this further.