# Pen Register A pen register historically captured numbers dialed from a telephone. In modern law the term extends to dialing, routing, addressing, or signaling information associated with wire or electronic communications, excluding content as defined by the statute. ## Notebook evidence [[Scanned_20260730-1830]], PDF pages 6–7, places pen-register language near call-detail records, probable cause, and FISA. These should not be treated as one authority: the legal showing and data category depend on the specific statute and order. ## Pair [[Trap and Trace Device]] records analogous incoming signaling information. Both are metadata-oriented concepts, but “metadata” is not a magic boundary: technical fields and aggregate patterns can still be highly revealing. ## Source - [[Scanned_20260730-1830]], PDF pages 6–7.