alarm/security system: active or not (call alarm/security company for filter instructions) utilities: does the meter report by phone? filter must be provided by utility company water gas electric paging or intercom system that uses phones: may require a whole house filter (POTS splitter) or separate line for dsl rollover lines: put the dsl on your fax line, not one of the rollover lines
satellite (and rarely cable) box may use phone for premium services, such as pay per view external ringer or light flasher distinctive ring
other phones: attic garage bedroom upstairs downstairs fax machine answering machine caller id box dial-up modem telecommunications device for the deaf (TDD)