Design of medium-speed data transmission system

Measurements and computations were employed to develop design principles for medium speed data systems. The assumption that errors would increase when the receive level falls below a certain threshold was confirmed. More errors occur when using switched connections than for leased connections. Noise disturbances produce single errors independent of signalling speed where as transmission interruptions are usually of longer duration, the number of errors increasing with signalling speed. Cyclic codes for checking are described which produce little redundancy and can provide any desired degree of protection.