Yes other devices can be connected to the T200I or T200E using the local Modbus port on the communications card. They will need to communicate using the Modbus protocol and the T200 will have to be configured as the master device and the devices connected to it will then act as slaves via the appropriate Modbus addresses.
For more information on T200I and T200E please click here
For more information on T200I and T200E please click here