During the continuance of a war in which the United States is engaged and when the provisions of this part are invoked, all communications common carriers shall comply with the following principles insofar as possible:

(a) Whenever necessary to maintain or restore a service having a designated priority, services having lower priority, lower subpriority, or no priority, will be interrupted in the reverse order of priority starting with nonpriority services.

(b) When services are interrupted to restore priority services, carriers will endeavor if feasible to notify users of the reason for the preemption.

(c) When public correspondence circuits are needed to satisfy requirements for priority services, idle circuits will be selected first. A minimum number of public correspondence circuits shall at all times be kept available so as to provide for the transmission of precedence-type messages and calls.

(d) Communications common carriers will not interrupt conversations having priority classification except insofar as necessary to restore services of higher priority.

(e) It is recognized that as a practical matter in providing for the maintenance or restoration of a priority service or services operating within a multiple circuit-type facility (such as a carrier band, cable, or multiplex system), lower priority, lower subpriority, or nonpriority services on paralleled channels within a band or system may be restored concurrently with higher priority services. Such reactivation shall not, however, interfere with the expedited restoration of other priority services.

(f) The Executive Agent is authorized to instruct the carriers on the percentage of government-switched network intermachine trunks to be restored to provide capacity for priority access line traffic.

(g) The carriers are authorized to honor NCS-certified priorities from other authorized carriers for leased facilities.

(h) The carriers are authorized to honor restoration priorities certified by the Executive Agent.

(i) To ensure the effectiveness of the system of restoration priorities established by this part it is essential that rigorous standards be applied. Users are requested and directed to examine their private line service requirements in light of the criteria specified in this part and with regard to the availability of alternate communications facilities such as public correspondence message services, and Government-owned emergency communications systems.