"Never-fail" audio response system

The Northwestern Bell Traffic Rating System is a real-time audio response dual computer system which must be on-line continuously. The system allows any Northwestern Bell long-distance operator to interrogate a remotely located computer system for a long-distance toll rate. The 3000 operators are widely scattered over an area covering 10% of the country. The toll message response consists of an amount, plus a word denoting whether the rate is for a "station-to-station" or "person-to-person" call. These conditions are ideal for using audio response for the remote display of information, rather than any of the commonly used hardware terminals.