Speeds in Signaling by the use of Light

Abstract

Relative Length of Dot, Dash and Space for Light Signaling.---A preliminary investigation was carried out to determine the relative lengths of dot, space and dash necessary for the greatest speed. Three observers made readings for this test and all agreed very well with the following ratio for the maximum speed: dot: dash: space:: 1: 4: 3.Speed for Sharp Cut-off of Signals.---To test out the speed for a sharp cut-off of the signals, using this ratio for dot, dash and space, a sector was made with which seven different signals could be shown. This sector was mounted so that the observers saw the light source through a small opening. According to the criterion adopted, speeds were obtained that would correspond to 9 to 13 five-letter words per minute.Speeds of Reading under Various Conditions.---It was shown that different observers were able to read the different signals at about the same speed with signals that were sharply cut off (as with the sector) and when the signals were made by turning on and off a special ribbon lamp filled with argon gas. The speeds of reading using other types of lamps were slower than for the ribbon lamp. With the observers at a distance and the lamp in a signalling unit, speeds somewhat slower were obtained. When an observer failed to read a given signal correctly the failure was generally due to his inability to see the dots.