For anyone considering a low budget PLC, I would recommend that you stay away from the Teco SG2 series of PLCs from factorymation.com. Specifically the modbus doesn't work properly and no one seems to know how to fix it. I've tried four different 485 adapters, numerous wiring combos and all without any luck. Also, these units can not be configured to work with anything other than 38,400-n-8-2 - so if you are at 9600 or some other rate you won't be able to make this PLC work with your other devices. The modbus documentation (translated Chinese) is of poor quality and support is also non-existent.