The DP/PA Link coupler bridges a PROFIBUS DP RS-485 backbone to a PROFIBUS PA MBP segment, handling the rate adaptation (1.5 Mbps to 31.25 kbps) and providing the intrinsically safe power supply for the PA segment.

A DP/PA Coupler combines several functions: rate bridging (high-speed DP towards low-speed PA), bus powering of the PA segment (the coupler supplies the DC voltage carrying both power and signal to the transmitters), intrinsic safety isolation (the Ex ia/ib barrier when feeding an explosive zone) and diagnostics (local signalling plus an upstream report on the DP side). Common products are the Siemens DP/PA Link, the Pepperl+Fuchs Active Field Splitter and the Stahl IS solutions, with a typical cost of 1-5 k euro per coupler.

Specify the coupler model based on the Ex zone classification, not just the device count: an Ex ia coupler is mandatory inside the hazardous area, even if the headline channel count looks identical.