"In the old days you put a coin into a jukebox, made your selection, and a plastic disk, called a record, was dropped mechanically onto a rotating platform, called a turntable. A needle with an electric pickup was lowered into the groove of the record, and there was music.
"Today, some jukeboxes are seen as well as heard. With the drop of a coin, magnetic video tape drives both a stereo sound system and a video projector == and in a few years, when they become less expensive, laser disks may be used as the storage medium.
"To control these more complex systems, engineers have replaced the gears and pulleys of the jukebox of yesteryear with microprocessors. One such operational video jukebox, made by Video Music International Inc. of Los Angeles, Calif., has a proprietary 8-bit microprocessor that translates the customer's song selection into two addresses on the video tape == one for the start of the video segment, another for the end.
"The microprocessor then controls motors that wind or rewind the tape to the starting point. The video tape has one video track and three audio tracks == two for stereo music and one that holds electronic pulses. The electronic pulses act as the electronic analog to sprockets on the two sides of motion-picture film, guiding the film forward or backward. The microprocessor counts the electronic pulses to determine where the next selection can be found on the tape.
"Each time a new video tape is loaded into a jukebox, the information from a portion of tape at the beginning is stored in the microprocessor 5 random-access memory, providing the microprocessor with an electronic Index of the locations of all the selections on the tape.
"The microprocessor also coordinates a second video- tape machine in the jukebox. This machine, which has background music, is activated between selections, when the customer is waiting for the first tape to wind to the next selection.
"In future models, the second machine will be used to project advertisements, which will run continuously until a customer puts $.50 into the machine to play songs."
Dave Morton (email@example.com)
IEEE/Rutgers Center for the History of Electrical Engineering