Sorry to cause confusion, having included those lines of code in the Citect.ini file has solved all the issues. I was picking brains to understand why without those lines of code, communication was still possible in one direction. The recent screen shots were of the fixed configuration, with the updated Citect.ini file, in contrast to the earlier screen shots with errors, and without the manual editing of the Citect.ini file. The problem has been solved on the bench, although we install next week... Cheers, Adam