Nearly all the points on the railway are mechanically operated by solenoid point motors, triggered remotely from the control panels by pressing buttons or touching a metal stud with a probe.

Power is supplied to the motors from Capacitor Discharge Units (CDUs) which, when triggered, provide a powerful momentary pulse capable of changing two or three points at once. This is preferable to using, for example, the standard 16 volt supply from a transformer which may not provide the power required and could also permit a continuous high current to flow through the solenoid coils, damaging them or even burning through the wires.

In a number of locations point motors are wired together, for example where the movement of one point must logically be complimented by the movement of another to prevent a derailment.

For many years there were only two CDUs; one for Grey Havens and the other at Michel Delving for the rest of the railway. There were two drawbacks to this configuration:

• Firstly the CDU at Michel Delving was physically some distance from a number of the points (particularly those at Buckland and Tuckbrough) and resistance losses in the long cable run reduced the power available to operate the motors. This meant some motors were unreliable and would not always change the point, especially if the CDU’s capacitors had not fully recharged after their previous use.
• Secondly, each point could only be controlled by one panel. A single operator wanting to operate a point at the other end of the layout had to crawl under a baseboard to reach the relevant panel.

Furthermore there was a desire to add some sort of automation or computer control to the railway, and to address these issues a new control system called CBUS is being installed...

CBUS

The CBUS layout control system is being developed by MERG (the Model Electronic Railway Group), and is a networked modular system comprising of input and output modules communicating via a pair of wires. Commands are transmitted across the network and modules can be taught to respond in different ways, such as operating points, signals, lights and LEDs, as well as providing feedback commands such as point position and track occupancy. A USB module enables a connected computer to send and receive data, permitting software programs to run as virtual control panels or automate the layout. Also under development is a CBUS DCC module.

For operation of points two types of module are required: a CAN_ACE3 to encode the button presses from a control panel, and a CAN_ACC4 which will independently control four solenoid point motors. The CAN_ACC4 is a CDU which can interpret up to thirty two custom messages and change any or all of the attached point motors. One of the many properties of the CBUS system is that one message can make a number of CAN_ACC4 modules respond: in other words, pressing one button can set an entire route by changing multiple points.

The existing point control wiring between the five control panels and the layout is being gradually replaced with the CBUS system, with Grey Havens, Bree and Rivendell stations now converted. This involves the removal of the existing point wiring, the installation of a CAN_ACE3 module at each control panel, and installation of a number of CAN_ACC4 modules near the points. The modules are then linked together with a two wire data cable, provided with a power supply and programmed from a computer.

When complete every powered point on the railway will be controllable from either its local control panel or from a computer (or tablet) connected to the CBUS network. Also, because there will in effect be lots of CDUs distributed around the railway, the operation of the points will be far more reliable. Further developments will add feedback concerning the position of the points and track occupancy, and may lead to the introduction of DCC locomotive control.