Some recent developments in data transmission

Much development has taken place recently in the use of the telephone system for data transmission. Special precautions have to be taken to minimize effects of certain characteristics of the telephone system and two types of modulation in current favour are reviewed in some detail. The division of responsibility between the data terminal manufacturer and the communication authority requires the definition of a standard interface between the data terminal and modem. A typical range of data transmission systems designed to meet this interface specification is introduced. The extension to broadband systems and the use of error correction and error detection systems are also discussed.