CBUS is a highly flexible, adaptable and modular model railway layout control system designed, developed, tested and used by members of MERG (Model Electronic Railway Group).

Set up in 1967 MERG is an international group, based in the UK, which promotes the use of electronics and computers in all aspects of railway modelling. Members are model railway enthusiasts who are interested in applying electronics to the operation of their model railways and the Group enables members to exchange ideas and information, and provides kits covering a number of interests including DC operations, DCC, Radio Frequency Identification, computer control and CBUS.

A CBUS installation consists of a number of modules which send messages to each other via a bi-directional local area bus network. A number of standard modules have been designed that carry out a range of tasks, including:

Modules are taught how to respond to messages transmitted across the network. For example a train detector can trigger a module to transmit a message implying a section of track is occupied which, via other modules, illuminates lights on a control panel, changes one or more points, changes the state of signals and closes the gates on a level crossing.

A CAN_ACE4 CBUS module
A CAN_ACE4 CBUS module, for operating point motors.

For basic, manual operation of points two types of module are required: a CAN_ACE3 to encode button presses on a control panel, and a CAN_ACC4 which independently controls up to four solenoid point motors. The CAN_ACC4, which operates like a Capacitor Discharge Unit, can interpret up to thirty two different messages and operate any or all of the attached point motors. Since one message can be acted upon by many CBUS modules, simply pressing one button can set an entire route by changing multiple points.

There are over 70 installed modules on the layout, with the possibility of more in the future. The following is a map of the installed network and its power supplies:

CBUS Module Map
CBUS module map showing layout of installed network