THE PEN REGISTER IS A DEVICE THAT LOGS NUMBERS DIALED FROM A PARTICULAR TELEPHONE BUT DOES NOT MONITOR CONVERSATIONS. A HISTORY OF THE USE AND INTERPRETATION OF SECTION 605 OF THE FEDERAL COMMUNICATIONS ACT OF 1934, WHICH LIMITS THE USE OF ELECTRONIC SURVEILLANCE, IS GIVEN AND SUBSEQUENT COURT DECISIONS CITING THE STATUTE ARE EXAMINED TO SHOW THE INAPPROPRIATE USE OF THE FOURTH AMENDMENT TO RESTRICT USE OF THE PEN REGISTER.