On this unit, FXS-1 has been set up to connect with a Freshphone 087- number and works 100%

This are analogue ports on this adaptor, FXS-1 and FXS-2.  

Can both of these be set up with the same number and password?

I tried to do this, FXS-1 says "Registered" while FXS-2 remains "Unregistered"

Thank you