The term "tie breaker" confused me too the first time I heard it.
My first thought was about a race...and my second was a smart-aleck thought about a circuit breaker wearing something around its neck.
You see them a lot in factories where there are 2 incoming lines from the power company for reliability.
The incoming equipment has a place at each end of a lineup for each line to land as well as breakers for the outgoing loads. In the middle is a tie breaker that connects the left and right ends of the bus together. There are almost always keylocks installed so that only 2 of the 3 breakers (Main-Tie-Main) can be closed at a time. If either incoming line fails you just open the main on that side, close the tie breaker and the whole lineup is live again.
