RS 485-IS Coupler - Safe in the field with the isolating transformer

The fieldbus isolating transformer RS-485-IS makes the PROFIBUS DP intrinsically safe. It can be used wherever communications exceed potentially explosive areas, i.e. above zone 1 or zone 21.

Area of application

The RS 485-IS coupler is used for connecting ET 200iS, ET 200iSP and other devices (e.g. OPs) in hazardous areas over PROFIBUS RS 485-IS and as a repeater for amplifying the data signals on bus lines. This is required when the maximum number of nodes or the maximum cable length per segment in the hazardous area is exceeded and a PROFIBUS RS 485-IS segment is connected to a PROFIBUS DP Ex i segment.


  • Plug and Play without the need for time-consuming circuit calculations and certifications (PROFIBUS International guidelines 2262)

  • Simple modification/expansion

  • Connection of numerous devices

  • Implementation as a barrier or repeater

Design and function

So that all the advantages of a failsafe bus installation are also available withPROFIBUS DP, an isolating transformer is used to make PROFIBUS DP intrinsically safe. This is done by isolating the bus and limiting the energy in the safe area. The fieldbus isolating transformer is used here as a barrier that converts PROFIBUS DP to an intrinsically safe PROFIBUS DP. It allows the PROFIBUS connector to be disconnected and connected even under Ex conditions.

The RS 485-IS is approved for use in hazardous areas of Zone 2; for this it must be mounted in a casing with a degree of protection of at least IP54. A manufacturer compliance notice for Zone 2 must be available (according to EN 50021) for the casing and the required cable glands. The device can be mounted horizontally or vertically on a S7-300 standard rail.