This instrument is only an display that shows data coming from another device that does the actual measurements. One of the reasons why the threewire synchro in

This instrument is only an display that shows data coming from another device that does the actual measurements. One of the reasons why the threewire synchro interface is used is that it is surprisingly accurate as long as you don't care about the fact that it is “slow” by modern standards. The same interface was used to direct artillery and similar things that require significant accuracy to be effective.