Measurement of telegraph distortion

The significance of telegraph distortion is explained by the aid of a notation in which changes from mark to space and vice versa, and changes of current from one value to another are regarded as the signals which compose a telegraph message. Reference is made to the use of an oscillograph for the measurement of telegraph distortion, and three machines better adapted to this purpose are described. One of these gives a permanent record and others use a stroboscopic method. In conclusion, mention is made of the method of determining the working margin of telegraph printers in terms of distortion.