Abstract: A passive data monitor and collection apparatus, and associated method, for obtaining market research data from an automated checkout system of a retail establishment. The apparatus positively monitors all the communications on a communications network between a plurality of point-of-sale terminals in a store and the store controller controlling the terminals. The store communications are converted from a phase encoded protocol into a standard RS 232 protocol which is then assembled into SDLC frames by a processor. The SDLC frames are separated on the basis of a control field format before being parsed by terminal addresses to form separate transactions on a list. The transaction list is produced by a real time monitor routine which builds the list from the asynchronous frames received from each of the store loops.