1. XRAY - Set only in secure harbors and naval facilities. All fittings marked XRAY (X) are closed at all times except when actually in use.
2. YOKE - Normal peacetime in port and underway cruising condition. All fittings marked XRAY (X) and YOKE (Y) are closed at all times except when actually in use. When open, the fittings should be so logged in the D.C. Closure Log.
3.ZEBRA - Set during peacetime emergency evolutions and war time battle situations. All fittings marked XRAY (X) YOKE (Y) and ZEBRA (Z) are closed, and may be opened only on receipt of permission from D.C. Central.
4.XRAY (X) - Closed at all times when not actually in use.
5.YOKE (Y) - Fittings for which alternate ZEBRA accesses exist. Normally closed when not actually in use, the only exception being when condition XRAY is set.
6.ZEBRA (Z) - Normally open for operation of the ship, habitability, and access. Closed during battle or emergency evolutions and conditions.
7.WILLIAM (W) - Ventilation and plumbing fittings normally open during all conditions of readiness.
Fittings that may be opened without special authority to allow the transfer of ammunition and the operations of vital systems.
CIRCLE XRAY
CIRCLE YOKE
CIRCLE ZEBRA
May be opened during condition ZEBRA on authority of the commanding officer, to allow the distribution of food, access to sanitary facilities, or ventilation of battle stations and other vital areas. When open, must be guarded for immediate closure if necessary.
BLACK D ZEBRA - Closed for darkening ship at night.
CIRCLE WILLIAM (W) - Nonvital ventilation and plumbing fittings normally open during condition ZEBRA, but may be close in the event of an NBC attack.
