I am using a magnetic card reader reading cards encoded with an 11 digit serial number followed by a carriage return. When swiping cards into a password or single line text field, the carriage return has the effect of trying to post the data but returns an error 4 message. If I change the field to a multiline text field it reads the data into the field and I can then submit the data manually. Any ideas why the carriage return doesnt post properly?

FMP relies upon the "Enter" key to exit the curent record (post the data) - NOT the "Return" key.

Your multiline text field is seeing the "return" and behaves accordingly (otherwise you could never get more than one line in a field)

Change the card reader trailing character to the"Enter" key.

Got about 9,000 library card users so dont think the university would be happy reformatting every card. I just need to verify the card number which allows them to vote in student elections. Have managed to get it working now but not without some weird goings on. Many thanks for the reply.