(1)
an emergency situation exists that involves—
(A)
immediate danger of death or serious bodily injury to any person;
(B)
conspiratorial activities characteristic of organized crime;
(C)
an immediate threat to a national security interest; or
(D)
an ongoing attack on a protected computer (as defined in section
1030) that constitutes a crime punishable by a term of imprisonment greater than one year;
that requires the installation and use of a pen register or a trap and trace device before an order authorizing such installation and use can, with due diligence, be obtained, and
may have installed and use a pen register or trap and trace device if, within forty-eight hours after the installation has occurred, or begins to occur, an order approving the installation or use is issued in accordance with section
3123 of this title.