Error correction in data transmission systems

The use of the existing telephone and telegraph networks as data transmission media is discussed with special reference to the correction of errors. These networks as they stand are far from ideal for data transmission because the high-level noise pulses and short interruptions which are relatively unimportant for normal usage cause errors in data messages. The data terminal equipment must contain some means of error correction, and various ways in which this can be done are explained. Typical error detection and correction equipments for both the telephone and telex networks are shown. Finally methods for the evaluation of the relative efficiencies of the various error correction and detection codes are described.