How do Modern Airliners get their heading information?

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Do modern airliners use flux vave as part of a Remote Indicating Compass (i.e. to give Heading Information)? Or they take that information from the IRU's ring laser gyros only? Micro-eletromagnetical systems?

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What about integrated standby instruments (ISIS)? They take the infomration from the same place or they are self contained and have dedicated gyros/MEMS?