Abstract: Methods and apparatus for solving the problem of non-uniform phosphor aging of the screen of a dual mode television receiver having the capability of displaying the picture image in two different aspect ratios, for example, 4:3 and 5:3. In one embodiment, the entire screen is illuminated during display of a 4:3 aspect ratio image on the central area of the screen so as to effect uniformity of aging over the entire screen. Alternatively, the areas at either side of the central 4:3 aspect ratio image area are not illuminated during display of 4:3 aspect ratio images but are, instead, post-aged following a period of display of such images. Another solution is to electrically compensate for the faster aging of the central 4:3 aspect ratio are of the screen when viewing 5:3 aspect ratio pictures.

Abstract: A television system for broadcasting high definition television on two channels of a direct broadcast satellite, a first of which carries a compatible 525-line picture. A second channel carries an augmentation signal, which in conjunction with the signal from the first channel, produces at a receiver tuned to both channels a 1050-line high definition television picture with a 5:3 aspect ratio. Time multiplex component signals and processing are employed, and high fidelity sound is provided by digital audio signals transmitted in time sequence with the video. There may be as many as five sound channels so as to provide three-channel stereophonic audio and various combinations of data and sound channels.

Abstract: Method and apparatus for detecting and significantly correcting bit errors in a pulse code modulated television signal which recognizes the unique spectral characteristics of isolated bit errors in a digital bit stream, which generate spectral energy outside the frequency band of the video signal, and utilizes that energy to detect and correct errors without the use of overhead bits.

Abstract: An apparatus and method for digitally encoding an NTSC color television signal in a manner that facilitates comb filtering of the digitally encoded signal. In accordance with the invention there is provided a means for generating a first sampling signal having a characteristic frequency of three times the NTSC color subcarrier signal. Another means is provided for generating a second sampling signal having the same characteristic frequency, this second sampling signal having its sampling reference points interspersed equally in time between the sampling reference points of the first sampling signal. Enabling means, responsive to the NTSC color television signal, are provided for alternately enabling the first and second sampling signals during successive horizontal scanlines of the television signal. Further provided is a means, responsive to the enabled sampling signal, for sampling the television signal. Finally, means are provided for converting the sampled television signal into digital form.