All two-way communication equipment carried on board craft
to which this chapter applies which is capable of automatically including
the craft's position in the distress alert shall be automatically
provided with this information from an internal or external navigation
receiver, if either is installed. If such a receiver is not installed,
the craft's position and the time that position was correct shall
be manually updated at intervals not exceeding 4 hours, while the
craft is underway, so that it is always ready for transmission by
the equipment.