Abstract: Apparatus for reducing interference in a first signal caused by a second signal. Before the signals are transmitted, the first signal is tested to determine how much interference can be tolerated. During portions of the first signal which can tolerate a large amount of interference, the amplitude of the second signal is increased. During portions of the first signal that can only tolerate a small amount of interference, the amplitude of the second signal is decreased. The average amplitude of the second signal is large enough to provide an acceptable bit error rate or signal to noise ratio, yet small enough not to substantially corrupt the first signal. In one embodiment, the technique is employed to allow transmission of additional data on a television channel.

Abstract: A graphic arts image comprising a plurality of regions, each region having a characteristic multilevel intensity, hue, texture or the like, is sampled and coded using samples along two consecutive scan lines. Individual code words are generated for the beginning, or head, of each run defining the start of a vein or boundary of a region of contiguous like-valued samples along each line and other code words are used for connecting information relating to samples on adjacent lines defining continuations of the boundary for the same region. Other code words identify the characteristic intensity or the like of the region, and a final type of code word identifies the end of the vein. Because the present method and apparatus advantageously codes each internal boundary between adjacent regions only once, an increase of efficiency by a factor approaching two is realized over techniques previously used.