I found in a book a scheme representing a terminal connection used in making an ammeter shunt (with the purpose of extending its measuring domain).
I can't understand what the drawing at b) represents. All those resistances want to model the contact resistances.
Then, the book says that in order to make the measurement more precise, we use a "double terminal", drawn here:
What do these drawings represent in real life and why are the resistances arranged as in the first picture, at c) (the delta connection)?