Modbus network controllers operate all the various options available on A2MC controlled machines. There are many different controllers and devices and options available. An A2MC system can be built up with as many or as few parts as required for the particular CNC system.
Note that there are two different Modbus network systems in use, MTA wiring and CAT5 wiring. The CAT5 system is more recent. Ensure you are choosing the correct parts for your wiring system. There are also CAT5 systems with clips which are electronically interchangeable with regular CAT5 system components.