SOMETIME in the middle of 1938, television sets may be put on sale in the is United States. The date is still a guess, but it is not unreasonable; it is the only guess made by experts in the field and they never use an earlier date; sometimes when a problem becomes difficult or an experimental programme shows up some weakness, the date is pushed farther ahead. As television will be, in effect, a combination of the radio and the moving picture, it has an exceptional importance; and since the early programmes of television will be based on the experiments now being made, the citizen may well begin to think about television now instead of neglecting it for twenty years as he neglected radio and the movies. Twenty years from now will be much too late for complaints.
There are three separate sets of problems in the launching of television: the problems of engineering, of financing, and of entertaining; and each of these will determine in part when television is to be started, for whose benefit, and with what materials.
About seven and a half million dollars have already been invested in experimental television and perhaps half a million will be spent annually before any income will appear. In return for this investment, the promoters have machinery which, they seem to believe, may be improved, but will not have to be fundamentally altered in order to give reasonable satisfaction. The potential buyer of a receiving set will not need to know the technical details of this machinery; he can be assured that any receiver he buys will give him the telecasts sent out by all the major systems of transmission. That is because the principal experiments now being made all use the same basic principle. In each one there is an apparatus usually called the 'scanner' which 'photographs' an object; in each one the lights and shades of the object are transformed into electronic impulses; these impulses pass through the air as those of ordinary radio do and the receiving apparatus turns them back into the highlights and shadows which compose a picture. Actually the picture is formed on the end of a cathoderay tube in the receiving set and we see it reflected in a mirror which becomes on a small scale our moving-picture screen. The areas of light and shade are traced with great rapidity in a straight line as if an invisible pencil were making lighter or darker dots, and a delicate mechanism sends the pencil back to the beginning of the line at the right moment; on the screen, which is about seven inches by ten inches, four hundred and fortyone lines are drawn for each picture. These pictures follow each other so rapidly that, by the persistence of vision in the human eye, they seem to be moving.