System and method for message exchange over a public-switched telephone network

摘要

Telephones are able to exchange arbitrary messages over a public-witch telephone network. Messages are created and sent to a switch. The switch transfers the message to a called party telephone. The switch sends data indicative of the end of the message to the called party telephone. Computers can send messages to telephones over the PSTN in this manner as well. Messages can be sent whether the called party is using the called party telephone or otherwise unable to immediately answer the called party telephone.