Comments by "Steve Valley" (@stevevalley7835) on "USS Balao - Guide 169" video.

@arthur_sarmento they originally used a slide-rule sort of device called an "is/was" In some films, you can see the "is/was", which, iirc, was generally round, hanging around the neck of the officer standing near whoever is calling out target range and speed from the periscope. The "is/was" was replaced by the Torpedo Data Computer, aka TDC. I think "Run Silent, Run Deep" or "Operation Pacific" has a couple looks at a crewman cranking the dials to set the computer for a calculation and a couple scenes where the TDC's remote terminal is used on the open bridge. The TDC terminal looks like a large pair of binoculars mounted on a swivel that is used to sight the target and send the bearing and range data to the computer.
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