S900 provides all input and output modules needed for intrinsically safe field signal connection. The field signals are amplified in every S900 functional module, electrically isolated, and then output via an internal serial bus. A communication interface converts the digitized signals to adapt them to the standardized PROFIBUS DPV1 fieldbus protocol. Supervisory process control systems, DCS or SCADA systems use an intrinsically safe fieldbus to communicate with the communication interface.

A single fieldbus network suffices for configuring the individual fieldbus nodes, for cyclic data exchange, for all acyclic services, and for communication with HART�-compatible field instruments. All functional modules can be replaced easily and quickly in the installation or maintenance phase. The functional modules and the � optionally redundant � communication interfaces of systems placed in Zone 1 can be removed and plugged in while operation is running, without affecting the communication of the remaining modules. Only the primary power for the plug-in type power supply modules requires increased safety EEx-e.

Integrated encapsulated switch-off mechanisms allow for hotswapping, i.e. the power supply units can be replaced without interrupting the primary power. Due to its little space requirements and robust design and its environmentally ruggedized case, the I/O system S900 is the best, cost-saving solution for use on site, in hazardous Zone 1 or Zone 2 areas.