A method of communications that is used in telephone systems and requires a physical transmission path — a circuit — to exist between the two devices wishing to communicate. The end-to-end path must exist before data can be sent. The only delay to which the data is subject is the propagation delay along the transmission medium (6 microseconds per 100 km for copper telephone lines). Since the path is reserved during the entire connection, any unused bandwidth is wasted. Compare message switching, packet switching, virtual circuit.