Shown here is one particular architecture for analog input modules. Here, the input signals are conditioned i.e. amplified, attenuated and level shifted, before being passed to an analog mux which then passes the signal to an ADC to be converted to a digital value. Here, the input channels which are connected to the field, are all isolated from the controller as a group. The controller, which is optional and may not exist on some I/O modules, is also isolated from the digital backplane used for communication. In addition to the isolated power domains, the interface between the A/D to the controller and the controller to the interface chip, typically SPI, is also isolated through digital isolation devices.