Experiments

Radio Television. Before the St. Louis section of the American Institute of Electrical Engineers, Consulting Engineer Ernst Frederik Werner Alexanderson of the General Electric Co. and the Radio Corporation of America, described his progress in the projection of motion pictures by radio. A central difficulty, the translation of optical images into electric current capable of impelling bands of ether waves, had already been surmounted by experimenters with the photoelectric cell and amplifier, used in motionless television and telephotography. Dr. Alexanderson's feat was to utilize a beam of light (which in motionless telephotography has from 2 to 20 minutes to trace and transmit the desired light-pattern or image) at unprecedented speed, so that it could render a complete image within the minimum time that the human eye will catch an image, a 16th of a second. This he had done by splitting his light beam into seven parts, letting each part trace a fraction of the whole image-pattern recorded by the photo-electric cell. The next problem was to transmit the seven fractional image-messages simultaneously upon high frequency ether waves. This Dr. Alexanderson had found still beyond the reach of practical radio, but calculated it could be achieved by the Hammond multiplex system (TIME, Oct. 26, 1925) using waves between 20 and 21 metres long. At the reception end, the multiplex message would be retransformed into seven beams of light which with proper synchronization, would reproduce the image-fractions. To throw these images together on a screen he had arranged 24 mirrors on the periphery of a swiftly rotating drum. The reflection of a series of rapidly changing images induced the optical effect of a moving picture, after the fashion of a cinema film. The possibilities: synchronized with sound-carrying radio, the sight-carrying radio might some day bring before the eyes of a man in Kankakee, Ill., the coronation of a king in Westminister;* it might enable folk to "go to the theatre" by turning a switch. Immediate possibilities: "air letters" (facsimiles) transmitted faster than they could be read; radio-cinema.

Seeing Things at Night. In London, Engineer John L. Baird, experimenter in wired television (TIME, Feb. 22), demonstrated his success at utilizing rays adjacent to the visible spectrum--invisible infra-red rays--to see things in complete darkness by mechanical means. The process involved isolating the invisible rays at their source (a special "search-light") and passing them through or to a medium that would render their effect visible. Since infra-red rays can be cast farther than any visible rays, and will penetrate fog and smoke more readily, the inventor predicted important military uses.

Crime Machines. Members of the New York Electrical Society watched Dr. A. P. Link of New York University attach an electrically-amplified stethoscope, developed by the Bell Telephone laboratories, to the chests of three young men, in turn. The third one had previously been sent from the room with instructions that one of them commit a "crime" (steal $10 from an overcoat upstairs). The stethoscope amplified the suspects' heartbeats 100,000 times, making them sound like pounded tom-toms. The "innocent" hearts beat steadily during questioning. The "guilty" speeded up, syncopated, despite its owner's efforts to stay calm. Another device spotted the culprit by flashing upon a screen a light which danced brightly when, during "guilty excitement," the electrical resistance of his skin was lowered.