Sharing fire-control data when a ship's own system is damaged

How can one ship transmit fire-control data to another whose own system has been shot out?

Older ships could fall back on displayed or signalled data and manual control; modern ships need pre-planned data-link integration.

The available fallback depends on the period and how much equipment survives aboard the damaged ship. Mechanical-era vessels could display information on fire-control clocks or flash it across by signal, then attempt to aim manually. Multiple fire-control sets provided redundancy, while individual turrets generally retained their own sights. Modern ships could theoretically connect a surviving weapon system to an allied ship's fire-control system through a data link. Such coordination needs compatible equipment and arrangements built in advance.