A320 FMGS position update logic

[simyoke]

A320 FMGS position update using multiple DMEs

Hello, gentlemen.

While reading A320 FCOM Vol. 1 I found a strange explanation as to the position update method of FMGS,

FCOM states that Each FMGS scans/tunes 5 DMEs. It sounds a bit strange since there are only 2 DME receivers on board A320,

How does an FMGS tune 5 DMEs with only 2 DME receivers?

[A and C]

As a pilot you can see and tune 2 DME,s the FMGS system has a further 3 DME systems at its disposal that it tunes at will to get the best position fix geometry.

[simyoke]

Thanks

Thank you very much for your answer.

FCOM mentions nothing about the additional 3 DMEs that are used for position update though.

Could you please refer me to the material( Where you found or heard) that has information on the additional 3 DMEs?