Patent GB-1235297-A (GB)
Title: Information retrieval and display system
IPC: G06F3/048
Filed: 1968-09-06
Abstract: 1,235,297. Cathode-ray tube displays. RCA CORPORATION. 6 Sept., 1968 [13 Sept., 1967], No. 42437/68. Heading H4T. A desired frame of video signals is selected from a plurality of available frames and supplied to storage device which is repetitively " read " the output signals produced thereby being supplied to a cathode-ray tube which repeatedly displays the selected frame in synchronism with the reading of the storage device. The invention is described in connection with a display system in which a particular frame of video signals, representative of e.g. stock market prices, may be selected from a plurality of frames conveying different information and repeatedly displayed at any of a plurality of viewing stations each of which may select a different frame. The information, comprising Alpha-Numeric characters &c., is displayed by brightness modulation (i.e. " on ", " off " control) of the beam of the display tube which is scanned in a conventional interlaced raster. Fig. 2 shows the system in schematic form. As shown, information produced by input devices 15 (e.g. keyboards) is stored in a bulk storage device 12 (e.g. a magnetic drum) as blocks of signals, each block containing the information of a complete (interlaced) television frame in the form of a succession of characters each specified by a six unit binary code. Also recorded on the device 12 are frame address signals, timing signals and signals specifying the number of characters per line and the number of lines per frame of the display. The device 12 carries twelve data tracks each consisting of six parallel data bit tracks and each data track contains 30 blocks of information which are read-out during one rotation of the drum which occupies one second. Other block loadings may, however, be utilized. In operation, the blocks are fed sequentially to a digital-to-video signal converter 11 which provides on twelve output channels, sequences of video signals together with the timing and other signals corresponding to the stored "blocks" " of information and these signals are transmitted over a wire or radio transmission channel to a plurality of similar stations 13. At the latter switch selection means 17 allows an operator to select one of the twelve channels in which it is known that a particular block of information is available and push-button selection means is then operated to produce a known binary number address which causes the display of an index frame (Fig. 4) showing the addresses of the various blocks in binary number notation. The push-button means is then operated to produce the binary number corresponding to the received block which is then displayed on television-type monitors or modified television receivers (in the case of a radio transmission channel). When the push-button means has been operated to set-up a particular binary address, selection circuits 17 operate to erase any information already stored in a frame storage device 19 comprising a single-gun, non-destructive read-out storage tube. This erasure is effective during two interlaced field scans (= one frame) of the tube after which the next frame of video signals is recorded on the tube and to allow of this operation the address of each frame is included in the block of information relating to the preceding frame. After the complete frame has been stored the tube is operated in a repetitive reading mode and the output signals derived thereby are fed to a cathode-ray tube display device 14 on which the characters defined by the signals are displayed repeatedly in synchronism with the reading of the storage tube. The latter may be repetitively read for about ten minutes without requiring refreshing which, when required, may be effected by again operating the push-button means to set-up the same binary address number. In this case any changes in the information stored in storage device 12 will be displayed. Alternatively, the circuit may be automatically refreshed periodically. The characters are produced by utilizing the video signals derived from the storage tube as bright-up pulses for a conventional raster of 525 interlaced scan lines per frame with a frame repetition rate of 30 per second. Fig. 1 shows the appearance of the characters each of which is produced in matrix of 5 x 7 dot elements by the application of selected ones of bright-up pulses XP1 to XP5 and XP0 to YP6, the latter comprising a and b pulses effective during two interlaced fields. To form aesthetically pleasing characters the pulses XP1 to XP4 are delayed to form pulses XP1d to XP4d which are selectively utilized to bridge over any gaps which would otherwise appear between the dot spaces. Details of the system are described with reference to Figs. 3a, 3b and 5 (not shown).