Digital data traffic recording unit for Integrated Services Digital Network (ISDN) has digital data recording unit is inserted in the phone line from a user terminal to prevent incorrect data being read out

摘要

A digital data recording unit (4) is inserted in the phone line (1) from a user terminal (2) to the public network (3) and has a D channel analysis module in a hard tamper proof moulded casing with supply from the phone line and three months storage of traffic data with infra red read out interface.