Duffer...
You don''t say whether you''re looking at a below-decks (''component type'') a/p or a cockpit mounted one. In either case, an a/p needs a flux-gate
compass (on older models, it could have been a different type) in order to orient the a/p. Below-decks units are sold in ''pieces'' and you must spec such a
compass as part of the package; tiller type & other cockpit mounted units have the
compass built into the unit (or its comes as a separate but included item, as with the CPT a/p).
Jack