thanks for your prompt reply. What I do not understand is the fact that the SGS Gas module does not require any periodicals to be connected while using the module. The original SGS instruction manual does not refer to a card reader. So it may be something else. The SGS MOD file from the HP41 library does not specify any special instructions on how to operate the program. And again there might be something else missing in the configuration of the go41cx or i41cx.