original_query: What is the purpose of a toll center in a telephone network?
query: What is the purpose of a toll center in a telephone network?
answer: A toll center (Class 4 office), also called a tandem office, routes calls between end offices that aren't directly connected or whose direct trunks are busy.  It's also used to connect to the long-distance network for calls incurring added costs, like operator-handled services.