US Patent 7616748 Central call screening system

A screening service for individual telephone lines to block unwanted calls based on call character signals and caller identification signals function in conjunction with a public switched telephone network. Calls identified by call character signals, as which identify a facsimile machine, and caller identification signals, as which identify an undesired call source, are recognized selectively in accordance with each program for individual telephone lines to provide blocking service including a termination cue. Using a dial-up connection, a subscriber can modify blocking information by a control program.