A period of national emergency shall be deemed to exist and the provisions of this part shall become effective only (a) after an attack upon the United States, or at a time specified by the authority of the President after such attack, and (b) by order of the Chair of the Board or his or her successor as set forth in §375.5, or when it is no longer possible to communicate with such official at his or her designated station.

[29 FR 15864, Nov. 26, 1964, as amended at 64 FR 66381, Nov. 26, 1999]