A system and method for characterizing phone calls in a public switched telephone network (PSTN), in order to identify Data Service Providers (as distinct from conventional telephone users). The system includes monitoring mechanism disposed at a first location (such as a central office or STP) for monitoring...http://www.google.de/patents/US6078647?utm_source=gb-gplus-sharePatent US6078647 - Method and apparatus for detecting a data service provider in a public switched telephone network
