Siemens analogue input modul sm 1231 series siemens 6es7231 4hd32 0xb0 the siemens 6es7231 4hd32 0xb0 is a din rail mounted analogue signal module that will convert analogue signals from the process into digital signals for internal processing by the simatic s7 1200 this signal module has 4 currentvoltage differential inputswith analogue signal modules users can optimally adapt their controllers even to more complex tasks if the task is expanded subsequently the controller can be upgra