"SP303 GSD.zip" This Zip File contains the gsd for the SP303 Spirax Sarco PROFIBUS PA positioner. The gsd file is a standard driver for profibus software configurators and "tells" the configurator how to handle the device in terms of "cyclic data exchange". You need to install this file if you use a configurator like Simatic Step7 (Siemens) while if you use a "manager" software like Simatic PDM you don't, in this latter case all you need is to install the ddl files. Installation procedure for .gsd file depends on the configurator used.