Recent Developments in the Measurement of Telegraph Transmission

This paper describes the progress which has been made in recent years in the development of methods and apparatus for the measurement of telegraph transmission in the Bell System. Such measurements play an important part in transmission maintenance work in the field and are also necessary in development work. The changes which have occurred in service requirements, particularly the large commercial development of start-stop teletypewriter service and the effect of these changes on the technique of telegraph transmission measurement, are first discussed; then a description is given of several new measuring devices and their use. TN keeping with advances in the telegraph transmission art, noteworthy improvement has been made in measuring devices and methods in the past few years. The faster, more accurate, and generally more dependable telegraph service now available has been made practicable not only by improvements in the telegraph systems but also by the use of improved measuring apparatus and techniques. In the early stages of development most transmission-measuring systems were arranged to measure transmission on " l o o p e d " circuits, that is, with sending and receiving terminals at the same point, so that a comparison between the sent and received signals could be made. Although such an arrangement is quite useful for laboratory testing, it imposes serious limitations on field testing. Therefore, it is generally desirable to make tests on a straightaway basis. For straightaway tests it is necessary to have at the receiving end certain information regarding the sent signals.