US3603965A

US3603965A - Information display circuit including means for blanking the display device

Info

Publication number: US3603965A
Application number: US705708A
Authority: US
Inventors: Arpad Somlyody
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1968-02-15
Filing date: 1968-02-15
Publication date: 1971-09-07
Anticipated expiration: 1988-09-07

Abstract

The disclosure is of a circuit which can be used in an information-handling and display system and includes a cathode glow display tube containing an anode and ten cathode electrodes which are coupled to a source of information signals in the system through a driving circuit. The driving circuit is a logic circuit which receives information signals from a decoder circuit and applies them to the cathode electrodes of the display tube, and the tube displays a number represented by the information signals when energizing potential is also applied to the tube anode. The driving circuit includes a control circuit which disables both the logic circuit and the display tube at desired times. The logic circuit includes five pairs of transistors connected in two groups with an auxiliary control transistor operating each group. The control circuit includes a transistor connected to the two control transistors for turning them off when desired to blank the display tube. A system is also disclosed for using the principles of the invention for controlling the timing of the application of information signals to the cathode electrodes and switching potentials to the anode electrodes of a series of display tubes in an informationhandling instrument.

Description

United States Patent DECODER Primary Examiner-John W. Caldwell Assistant Examiner-Marshall M. Curtis Attorneys- Kenneth L. Miller and Robert A. Green ABSTRACT: The disclosure is of a circuit whic can be used in an information-handling and display system a d includes a cathode glow display tube containing an anode and ten cathode electrodes which are coupled to a source of information signals in the system through a driving circuit. The driving circuit is a logic circuit which receives information signals from a decoder circuit and applies them to the cathode electrodes of the display tube, and the tube displays a number represented by the information signals when energizing potential is also applied to the tube anode. The driving circuit includes a control circuit which disables both the logic circuit and the display tube at desired times. The logic circuit includes five pairs of transistors connected in two groups with an auxiliary control transistor operating each group. The control circuit includes a transistor connected to the two control transistors for turning them off when desired to blank the display tube. A system is also disclosed for using the principles of the invention for controlling the timing of the application of information signals to the cathode electrodes and switching potentials to the anode electrodes of a series of display tubes in an information-handling instrument.

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momaom E265 wumaom mmm zutzm utzm 555 Qmw 6mm QmN QwN Numb-2300 62 E INFORMATION DISPLAY CIRCUIT INCLUDING MEANS FOR BLANKING THE DISPLAY DEVICE BACKGROUND OF THE INVENTION Indicator tubes of the type manufactured by Burroughs Corporation and known as NIXIE tubes have been widely used in information-handling systems such as computers, calculators, and the like. Under some circumstances, it is desirable to positively hold off or turn off the display tube while other parts of the system perform an operation or while information signals are collected for application to the logic driver circuit for the display tube. Various circuits have been proposed for turning off or blanking a display tube; however, these circuits are not completely satisfactory since they generally operate directly on the display tube itself, and not the associated logic circuitry. In addition, these circuits are not suitable for use in complex systems such as computers or calculators.

SUMMARY OF THE INVENTION Briefly, a circuit embodying the invention includes one or more display tubes of the type described above and a separate logic circuit for applying informations signals to each display tube. The circuit also includes auxiliary circuit means for disabling the logic circuit (s) and the display tube(s) at a desired time in the information-receiving and displaying operation DESCRIPTION OF THE DRAWING In the drawing:

FIG. I is a schematic representation of a circuit embodying the invention; and

FIG. 2 is a schematic representation of another system embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The principles of the invention are applicable to information-handling circuits and systems which display information in a display device such as a type 6844A numerical indicator tube. Thus, the invention may be used in a relatively simple circuit such as a decoder or in more complex systems such as computers, calculators, or the like. One type of circuit (FIG. I) which may utilize the invention includes various information-handling circuits represented by block which feed into a decoder 30 and a display driver circuit 40. The display driver circuit 40 includes a display tube 50 and a logic driver circuit 52 for applying thereto the output of the decoder 30 to cause a number to be displayed in tube 50.

The indicator display tube 50 is a gas-filled tube and includes 10 glow cathodes 57 in the form of numerals zero to nine and an anode electrode 58. When a positive potential of about 150 volts is applied between anode 58 and a cathode numeral 57, the cathode exhibits cathode glow. A driver or switch 59, which may be an electronic switch such as a transistor, is coupled to anode 58 to apply operating potential thereto at the same time that information potential is applied to a cathode numeral.

For purposes of illustration, the decoder 30 is shown as a type which has seven output lines which carry signal bits having a meaning in decimal code, that is, representing a decimal number. Five lines 32 comprise signal information lines, and two lines 33 comprise signal control lines.

The logic driver circuit 52 for coupling signals from the decoder 36 to tube 59 includes 10 signal-receiving and registering active devices 60 to 69, which may be tubes, transistors, or the like. These transistors may be referred to as glow transistors since they are coupled to the respective glow cathodes. For purposes of illustration, three-electrode transistors are shown with the electrodes thereof represented in conventional fashion. As shown, the devices 60 to 69 are arranged in two groups of live and in pairs, with one member of a pair being in each group. Thus, one group includes devices 60 to 64, and the other group includes devices 65 to 69, with the pairs being 60-65, 62-67, 63-68, 64-69. In addition, two auxiliary devices 72 and 74, also transistors, are provided to control the operation of the two groups of five transistors.

The five transistors 60 to 64 have their emitter electrodes connected together to a bus which is connected to the collector electrode of control transistor 72, and the five transistors 65 to 69 have their emitter electrodes connected together to a bus 84 which is similarly connected to the collector of control transistor '74. The collector electrodes of the transistors 60 to 69 are each connected by leads 89 to one of the cathode numerals in tube 50. The emitter electrodes of the two control transistors 72 and 74 are connected together to a bus 90.

According to the invention, an auxiliary control circuit 94 is provided including an auxiliary control transistor 10%) which has its collector electrode connected to the emitter electrodes of the control transistors 72 and 74 and its emitter electrode connected through a Zener diode to ground. Control circuit 94 also includes a source of clock pulses or control pulses coupled through a resistor and diodes M0 and (oriented as shown) the base of control or blanking transistor 100. The base of transistor 100 is also coupled through a resistor to ground, and junction point 18!) of the

diodes

140 and 150 is connected through a capacitor to ground. A positive DC power source Vll is connected through

resistors

200 and 210 to line 33 and junction point 180, respectively, and through resistor 220 to the collector of transistor lllll. Other connections are made to provide bias voltages for the various transistors as shown and need not be described in detail. In circuit 94, capacitor 190 extends the time duration of pulses from source 120, and the

diodes

140 and 150 adjust voltage levels between source 120 and the base of transistor 100. Under some circumstances, each diode 140 and 1150 might require additional diodes to provide the desired balance, or, in some cases, no diodes may be needed.

In operation of the circuit 10, signal information is processed .through

circuits

20 and 30, and a group of signal bits appears on the seven lines 32 and 33. Normally, transistors 60 to 69, 72, and '74 are held off by the bias voltages applied. Each group of seven signal bits has such polarities that the base electrodes of only one pair of transistors (ill to 69 receive a positive turn-on signal and only one of the control lines 33 receives a positive turn-on signal. The positive signal applied to the control line 33 turns on one of the control transistors, and this in turn applies a generally negative potential to one of the

buses

80 or 84, and this permits one transistor of the selected pair to turn on. When the selected transistor turns on, the cathode numeral in tube 50 to which it is connected glows and is visible when switch 59 is closed. As a specific example, if positive potential is applied to the bases of

transistors

60 and 65 and to transistor 72, then transistor 60 is turned on and numeral O glows.

Auxiliary control circuit 94 is used as follows. It has been found that, under some circumstances, particularly during the time when signal information on lines 32 and 33 is changing from one combination to another, improper operation of tube 50 may result and two cathodes may glow. This is prevented by the operation of the invention, In addition, the invention can be used to positively disable the circuit and the display tube 50. This is accomplished, according to the invention, by a negative pulse 121 being coupled from source 120 through the resistor I30 and

diodes

140 and 150, to the base of auxiliary control or blanking transistor 100 which is normally on and is now turned off. This results in the application of positive potential to the emitter electrodes of the control transistors 72 and 74 which are also held off. Thus, a generally positive potential is applied through the

buses

80 and 84 to the emitters of the five pairs of transistors 60 to 69 which are also held off. Because all of the driving transistors 60 to 69 are immobil' ized, the indicator tube 59 is blanked or held off and no cathodes can glow.

In the circuit, the resistor 130 and capacitor 190 provide a time constant which determines the time duration of the control pulse 121 and the length of time the circuit is disabled. In general, it is desirable for the pulse to be terminated just after a new group of signal bits appears on the lines 32 and 33 to the transistors 60 to 69 and 72, 74 so that the information can be displayed in tube 50 without spurious glow.

The principles of the invention may also be used in a somewhat more complex system of the type illustrated in FIG. 2 which represents a portion of a computer, calculator, or the like in which information is displayed on a plurality of

display tubes

50A, 50B, 50C, as is well known. In such a system, a single decoder 30 and logic driver circuit 52 are provided for all of the display tubes, and each of the 10 output lines 89 from circuit 52 is connected to the same cathode numeral in the display tubes 50. Signal information is processed through the circuit and appears on lines 89 serially; that is, the first group of signals representing a decimal number is intended for entry in the first tube in the series 50A, the second group of signals is intended for entry in the second tube 508, etc. In addition, an electronic switch means or

driver

59A, 59B, 59C is provided in the anode circuit of each tube 50.

A ring counter 250 is coupled to and operates each of the anode drivers 59 by leads 260, and it is assumed that the signal source represented by block includes in its circuitry a sequential memory or register from which information signals are fed along toward the tubes 50. Both the ring counter 260 and the memory or register in source 20 are coupled to the output of pulse source 120 by leads 270 for synchronizing the operation of

switches

59A, 59B, and 59C and their associated display tubes with the operation of source 20 and of decoding and driving circuits 30.

In operation of the system 10, the first pulse 121 from source 120 operates ring counter 250 and causes the counter to apply operating potential to the anode of tube 59A. At the same time, the memory or register in signal source 20 is energized by the first pulse 121 and caused to transmit the first group of information signals through the circuit in the direction of the indicator tubes. Again, at the same time, the first pulse 121 energizes control circuit 94, and this circuit, as described above, disables logic driver circuit 52 and all of the indicator tubes for the length of time which is required for the information signals to reach lines 89. At the end of this time period, again as described above, the pulse 121 is terminated and logic driver circuit 52 is permitted to operate and apply operating potential to one of the cathodes in tube 59A determined by the first group of information signals. This selected cathode exhibits cathode glow, and the proper numeral representation appears. The next pulse 121 repeats this cycle of operation for tube 59B, and the third repeats the cycle of operation for tube 59C, etc.

The above-described operation occurs continuously and at such high repetition rate that all numbers corresponding to input information signals are visible in their tubes 50 at the same time.

According to the invention, control circuit 94 insures the proper coordination between the feeding of information to a series of display tubes and the operation of these tubes. In the circuits described, if control circuit 94 were not provided, spurious display might result. Such spurious display occurs when, for example, tube 59A is on and displaying a numeral and another group of information signals appears on lines 89 before tube 59A is turned off and the next tube 59B in the series is switched on. When this happens, tube 59A displays two numbers. This spurious display is prevented by the invention.

I claim:

1. In a decoding system for driving at least one multiple cathode display device for displaying information thereon, including a plurality of glow transistors coupled to different cathodes, said glow transistors being arranged in at least two groups, and a plurality of auxiliary transistors, one auxiliary transistor coupled to each group for rendering said groups of transistors conductive or nonconductive when said auxiliary transistors are conductive or nonconductive, respectively, the improvement of a blanking circuit comprising:

a blankin transistor, said blan mg transistor being connected to like electrodes of said auxiliary transistors for enabling said auxiliary transistors to be conductive or nonconductive when said blanking transistor is conductive or nonconductive, respectively, and

means operating independently of said information for selectively switching said blanking transistor between said conductive and nonconductive states,

said switching means being adapted to render said auxiliary transistors nonconductive during the time when a change occurs in said information.

Claims

1. In a decoding system for driving at least one multiple cathode display device for displaying information thereon, including a plurality of glow transistors coupled to different cathodes, said glow transistors being arranged in at least two groups, and a plurality of auxiliary transistors, one auxiliary transistor coupled to each group for rendering said groups of transistors conductive or nonconductive when said auxiliary transistors are conductive or nonconductive, respectively, the improvement of a blanking circuit comprising: a blanking transistor, said blanking transistor being connected to like electrodes of said auxiliary transistors for enabling said auxiliary transistors to be conductive or nonconductive when said blanking transistor is conductive or nonconductive, respectively, and means operating independently of said information for selectively switching said blanking transistor between said conductive and nonconductive states, said switching means being adapted to render said auxiliary transistors nonconductive during the time when a change occurs in said information.