Inventors: Leonard Wintfeld and Robert H Nagel

US patent number:4,135,213

US patent application date: April 23, 1976
US patent issue date: January 16, 1979

SYNOPSIS OF THE INVENTION

This invention provides a real time frame grabbing video display terminal for substantially instantaneously providing a continuous direct video display of a selectable predetermined video frame of information on a video display means, such as a cathode ray tube.

The display is provided from continuously receivable information which has been remotely conveyed over a transmission media, such as a conventional television distribution system. It is provided in a manner in which the operation of the terminal is controlled by a microcomputer means, such as a central processing unit contained on an integrated circuit chip.

This microcomputer has been operatively connected to the transmission media for receiving the continuously receivable information.

This information comprises a plurality of pseudo video scan lines, each of which has a television video scan line format and is capable of comprising a complete self-contained packet of digital information sufficient to provide an entire displayable row of video data characters. Each of the pseudo video scan lines has an associated transmission time equivalent to the television video scan line with the packet of digital information comprising at least address information for the displayable row and data information for the displayable characters in the displayable row.

The microcomputer loads the local storage means with the displayable video row data when the first predetermined output condition is provided thereto. Each of the pseudo video scan lines received by the terminal preferably comprises a horizontal sync signal at the beginning thereof which provides a record separator between adjacent pseudo video scan lines and insures that any loss of synchronization or noise pulse will not disrupt more information than one pseudo video scan line.

Furthermore, each of these pseudo video scan lines preferably comprises a three level signal having first, second and third signal levels with each of the packets of digital information varying between the second and third signal levels and the horizontal sync signal information being provided between the first and second signal levels.

Significant data compression in transmission time of the signals received by the terminal is obtained due to the transmission of pseudo video scan lines as opposed to conventional television scan lines since each pseudo video scan line is a self-contained packet of information sufficient for display of an entire displayable video row containing a plurality of conventional television scan lines, such as 13, as opposed to display of one television scan line.

The local microcomputer, operates in conjunction with the keyboard which provides the information request, and enables updating on a row-by-row basis as opposed to a page-by-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.