GB1446686A - Information display apparatus - Google Patents

Abstract

1446686 Alpha-numeric displays and circuits therefor NCR CORP 17 Sept 1974 [26 Oct 1973] 40434/74 Heading G5C [Also in Division G3] Apparatus for displaying a number of digits sequentially and in significant order on a single digit display device 49, e.g. of l.e.d. type, comprises means for blanking the display between individual digits for a period greater than one eighth of a second, the digits each being displayed for between one eighth and one half of a second. A clock or watch is described in which six sequentially displayed digits give the time in hours, minutes and seconds. Timing signals are derived from a 60 c/s. source 1 and fed to the display by a specified dividing and coding I.C. 44 and logic inverters 45-48. The coded signals for the six digits are multiplexed at 1000 c/s. The circuit 44 also produces one of six signals to designate which digit is currently available at the coded outputs, the six signal outputs being connected via inverters 50-55 to NAND gates 56-61. The NAND gate outputs are all connected to a 4-bit latch circuit input of the display 49, this circuit preventing the introduction of new information to the display except when a strobe pulse is present at its input. The other inputs of the NAND gates 56-61 are connected via inverters 63-68 to selected ones of sixteen outputs #T0-#T15 which are sequentially energized for about “ second each. This energization is achieved by the use of NAND gates 26-41 which have four inputs fed via inverters 10-25 and 43 with signals derived from the source 1 by sequential binary dividers 2-9. The six digits are thus displayed in order, commencing with the tens of hours. Blanking between digits is achieved by connecting the remaining ones of the outputs #T0-#T15 to a NOR gate 62 the output of which is taken to a blanking input of the display 49. The display is thus blank for one time period T1 between the hours digits, for two periods T3, T4 between the hours and minutes, and similarly for the minutes and seconds. Finally there are three blank periods T13-T15 before the cycle recommences. Switches 69-71 allow the hours and minutes to be advanced rapidly for setting, or the internal time count to be held. The source 1 may be a relaxation oscillator or a crystal oscillator with dividers, or may be coupled to a mains line. Different lengths of the various blanking periods are envisaged for other applications, e.g. to display social security or telephone numbers in, e.g., two and/or three digit bursts.