Capabilities of the Telephone Network for Data Transmission

The telephone industry has a long history of providing data transmission services. Over the years many varieties of service offerings making use of the range from narrow-band telegraph 1 channels up to 4-mc video channels have been provided. Such services usually have been provided on a private line basis by adapting regular telephone facilities to the particular data service requirement. The increased use of computers and automatic data processing systems in the commercial, industrial and military areas has substantially increased the demand for greater varieties of data services and data transmission channels. This expansion, with its attendant requirement for a variety of speeds and channel usage time, has encouraged development of service offerings that use the regular switched message telephone network in establishing the communication channels. In the Bell System this service concept has been given the name of Data-Phone,* which * Data-Phone is a trademark of the American Telephone and Telegraph Company identifying Bell System equipment used in this Bell System service. 431