an Entity references as follows:
A flight computer is a form of circular slide rule used in aviation and one of a very few analog computers in widespread use in the 21st century. Sometimes it is called by the make or model name like E6B, CR, CRP-5 or in German, as the Dreieckrechner. (Electronic option is available and can be used on FAA exams but pilots are still expected to know how to use the analog version.)