Telegraph Transmission Testing Machine
F. B. Bramhall · Transactions of the American Institute of Electrical Engineers · 1931
In the study of telegraph transmission efficiencies and the analysis of signal distortions a suitable signal recording device is a first requisite. This paper describes a machine developed for the purpose. This machine furnishes a graphical and permanent record of the received signals and shows their relation to sent signals, in a form which is most convenient for comparison and analysis. The unusual arrangement of the recorder is such as to adapt it especially to the study of both characteristic and fortuitous distortions and, in general, to the comparison and absolute measurement of short time intervals. Time intervals of one ten-thousandth of a second in the opening and closing of electrical circuits are graphically recorded without resort to photographic means.