What is the Intermarket Trading System ?

The Intermarket Trading System is the electronic communications network linking the trading floors of 7 registered exchanges to permit trading among them in stocks listed on either the New York Stock Exchange or Amex and one or more regional exchanges.
Through the Intermarket Trading System , any broker or market maker on the floor of any participating exchange can reach other participants for an execution whenever the nationwide quote shows a better price available.
A floor broker on the exchange can enter an order to assure execution of all of an Intermarket Trading System offering or bid, instead of splitting it with competing brokers.