Inventors: Richard Saylor and Robert H Nagel

US patent number:RE31,863

This a reissue of patent 4,042,958.

US patent application date: September 10, 1975
US patent issue date: August 16, 1977

SYNOPSIS OF THE INVENTION

Within this system, information is transmitted in rows, or a plurality of pseudo video scan lines. A real-time frame grabbing system is provided for a largely instantaneous provision for a continuous video display of a selectable predetermined video frame of information on a video display from continuously transmittable video information.

Each of these scan lines has a television video scan line format. Each line comprises a complete and self-contained packet of digital information sufficient to provide an entire display of video data characters. These scan lines have an associated transmission time equivalent to that of a conventional television video scan line. The packet of digital information comprises at least address information, such as page, group, permission, user and direct address for a displayable row and data information for the displayable characters, such as 32 characters, in a displayable row.

Each of the pseudo video scan lines further comprises a horizontal sync signal at the beginning thereof, each horizontal sync signal providing a record separator between adjacent pseudo video scan lines as well as providing noise immunity on a row by row basis for resetting all the input logic in the receiver which processes the transmitted signal every horizontal sync pulse.

Each of the packets of digital information contained within the pseudo video scan line, also preferably includes an error check information content based upon at least the address and data information content of the associated pseudo video scan line, the receiver including error check means for obtaining an error check indication of the distributed associated pseudo video scan line and comparing the error check indication with the error check information content of the associated pseudo video scan line in accordance with a predetermined error check condition for providing a predetermined output condition when the error check condition is satisfied.

The receiver also includes condition responsive means operatively connected to the error check means for preventing the provision of the displayable video row from the associated pseudo video scan line when the predetermined output condition is not met.

The system also preferably includes programmable means, such as a general purpose computer, for receiving the continuously transmittable video information, retrievably storing this information, reformatting it into a desired pseudo video scan line format and continuously providing this reformatted information to the transmitter on a word-by-word basis, a word comprising a pair of displayable characters.

Furthermore, the programmable means preferably includes means for interleaving the reformatted pseudo video scan line information to provide pseudo video scan line information corresponding to a common assigned row for a plurality of frames to the transmitter before providing pseudo video scan line information corresponding to a subsequent different common assigned row for the plurality of frames to the transmitter.

Thus, the provision of the pseudo video scan line enables the use of conventional television transmission techniques and equipment for transmission and reception as well as conventional television circuitry for processing the received and transmitted signals.

In the present invention, frame grabbing is accomplished by preferably feeding the pseudo video scan line into a buffer storage for comparison with an information request from the keyboard which, if matched, updates the appropriate memory for display or selection control so that updating is, in reality, accomplished on a row-by-row basis as opposed to a page or frame-by-frame basis as new information is provided in real time, the selected frame being automatically updated in real time as new information is provided for a given row of the displayed selected frame.