A PC or other data terminal connected to the maintenance port of a PBX or key telephone system (KTS) in order that authorized users can access the system software for purposes that might include Move, Add, and Change (MAC) activity; Class of Service (CoS) changes; automatic route selection (ARS) programming; requests for traffic and usage statistics; requests for status reports; and diagnostic testing and analysis. Remote maintenance generally can be accomplished over the PSTN via a modem connection.