Changes and effect on compatibility1 Downwards compatible changes and fault repair with no effect on operation (e.g. spelling mistakes on display)2-_ Downwards compatible hardware and/or software change of interfaces:H HART® P PROFIBUSF Foundation FieldbusM ModbusX all interfaces3-_ Downwards compatible hardware and/or software change of inputs and outputs:I Current outputF, P Frequency / pulse outputS Status outputC Control inputCI Current inputX all inputs and outputs4 Downwards compatible changes with new functions5 Incompatible changes, i.e. electronic equipment must be changed