Apparatus for operating multiple position display tubes

Claim 2

A character display circuit comprising an envelope containing an ionizable gas, an anode and a plurality of cathodes within said envelope, each of said cathodes having the shape of a segment of a character to be displayed, circuit means for establishing a glow potential between said anode and different combinations of said cathodes for causing said different combinations of said cathodes to glow and thereby display different characters, said circuit means including a plurality of cathode drivers, one connected to each of said cathodes, and means for selectively energizing said cathode drivers to render their connected cathodes glowing, an auxiliary electrode in contact with the ionizable gas and in operative relation with said anode and cathodes and the circuit means so that the current through said auxiliary electrode is a function of the number of cathodes which are glowing, and bias circuit means for establishing a predetermined voltage on said cathodes when they are not glowing, including a resistance element for each of said cathodes, each being connected from a first terminal to a diffeRent one of said cathodes, the first terminals to which each of said resistances are connected all being at substantially the same voltage level, said auxiliary electrode being electrically connected to said first terminals for biasing said auxiliary electrode to said voltage level, at least one impedance device electrically connected to said auxiliary electrode, said cathode drivers being connected electrically across at least a portion of said impedance device by said resistance elements and serving to change the level of the impedance connected to said auxiliary electrode as each cathode driver is energized and its connected cathode rendered glowing.

Claim 3

A character display device as in claim 1 wherein the auxiliary electrode is connected electrically in common with at least one of said first terminals.

Claim 4

A character display device as in claim 2 wherein all of said first terminals are connected electrically in common.

Claim 5

A character display circuit as in claim 1 wherein said current in the auxiliary electrode passes to it from the anode through the ionizable gas, and at least a portion of said current passes through said impedance device and tends to increase the voltage on the auxiliary electrode as the number of glowing cathodes increases, and wherein the level of the impedance connected to the auxiliary electrode is reduced by the parallel-connected cathode drivers, as each additional cathode driver is energized, to compensate for the tendency of the auxiliary electrode to increase in voltage as the number of glowing cathodes increases.

Claim 6

A character display circuit as in claim 1 further including an anode voltage supply terminal and circuit means connecting said terminal to said anode, a cathode voltage supply terminal, with the cathode drivers being connected between the respective cathodes and said cathode voltage supply terminal, and wherein said impedance device comprises a voltage divider having a junction connected to said auxiliary electrode, a first predetermined impedance connected from said junction to said anode voltage supply terminal, and a second predetermined impedance connected from said junction to said cathode voltage supply terminal.

Claim 7

A circuit to compensate for voltage changes on an auxiliary electrode located in a gaseous atmosphere of a glow discharge indicator tube which has an anode and a plurality of cathodes in operative relative to it in the gaseous atmosphere, each of the cathodes being in the shape of a segment of a character to be displayed and being capable of exhibiting cathode glow when energized, comprising circuit means for energizing said anode and different combinations of said cathodes to display different characters, said circuit means including a plurality of cathode drivers, each connected to one of said cathodes and serving to energize the connected cathode to cause it to glow in response to an input signal, first bias circuit means for establishing a voltage on said auxiliary electrode, said bias circuit means comprising a voltage divider having a junction for connection to the auxiliary electrode, a predetermined impedance connected from said junction to a first reference potential terminal, and a second predetermined impedance connected from said junction to a second reference potential terminal, and second bias circuit means for establishing a bias voltage on said cathodes when they are not glowing comprising a plurality of impedance elements each connected from a junction of said voltage divider to a different one of said cathodes, each of said impedance elements being bidirectional in its impedance characteristics, the cathode driver and impedance element connected to each cathode being connected in series with each other across at least a portion of one of said predetermined impedances, to modify the effective impedance that is provided for connection to said auxiliary electrode as each of the cathode drivers responds to an input signal and caUses its connected cathode to glow.

Claim 8

A circuit to compensate for voltage changes on an auxiliary electrode located in a gaseous atmosphere of a glow discharge indicator tube which has an anode and a plurality of cathodes in operative relative to it in the gaseous atmosphere, each of the cathodes being in the shape of a segment of a character to be displayed and being capable of exhibiting cathode glow when energized, comprising circuit means for energizing said anode and different combinations of said cathodes to display different characters, said circuit means including a plurality of cathode drivers, each connected to one of said cathodes and serving to energize the connected cathode to cause it to glow in response to an input signal, first bias circuit means for establishing a voltage on said auxiliary electrode, said bias circuit means comprising a voltage divider having a junction for connection to the auxiliary electrode, a predetermined impedance connected from said junction to a first reference potential terminal, and a second predetermined impedance connected from said junction to a second reference potential terminal, and second bias circuit means for establishing a bias voltage on said cathodes when they are not glowing comprising a plurality of impedance elements each connected from a junction of said voltage divider to a different one of said cathodes, each of said impedance elements being bidirectional in its impedance characteristics, the cathode driver and impedance element connected to each cathode being connected in series with each other across at least a portion of one of said predetermined impedances, to modify the effective impedance that is provided for connection to said auxiliary electrode as each of the cathode drivers responds to an input signal and caUses its connected cathode to glow.

Claim 9

A voltage compensation circuit as in claim 6 wherein the plurality of impedance elements of the second bias circuit are connected to the junction that is provided for connected to the auxiliary electrode.

Claim 10

A voltage compensation circuit as in claim 6 wherein all of said impedance elements are resistors and the cathode drivers are transistors, and the plurality of resistor-transistor series circuits thus formed are connected from a junction of the voltage divider to one of said reference potential terminals.

Claim 11

A character display circuit for displaying any one of a plurality of different characters in each of a plurality of side-by-side character positions, comprising a plurality of anodes, one in each of said character positions, a plurality of groups of cathodes, each such group being associated with one of said anodes and being located in one of said character positions, each of the cathodes having the shape of a segment of one of the characters to be displayed, each of said anodes and its associated cathodes being disposed in an ionizable gas atmosphere at a pressure capable of sustaining cathode glow discharge, a plurality of cathode conductors each electrically connected to one of the cathodes in each character position, a plurality of cathode drivers, each electrically connected to one of said cathode conductors, for energizing said cathodes selectively in response to a first set of input signals, circuit means for selectively energizing said anodes, in synchronism with the selective energization of said cathodes, in response to a second set of input signals, for displaying selected characters in each of said character positions, an auxiliary electrode in the gaseous atmosphere associated with each character position, the current therethrough being a function of the number of cathodes which are glowing, first bias circuit means for maintaining an electrical potential within a predetermined range on said auxiliary electrode, said bias circuit means including a terminal at an initial voltage level electrically connected to said auxiliary electrode and at least one impedance device electrically connected to said terminal, and second bias circuit means for establishing a predetermined bias voltage on said cathodes including a plurality of circuits having bidirectional impedance characteristics, each containing a biasing resistance and being connected from the terminal of the first bias circuit means to a different one of said cathode conductors, and further circuit means connecting each of the cathode drivers and its connected biasing resistance across at least a portion of said impedance device, to reduce the effective impedance connected to said auxiliary electrode as each cathode driver energizes one of said cathodes.

Claim 12

A character display circuit for displaying any one of a plurality of different characters in each of a plurality of side-by-side character positions, comprising a plurality of anodes, one in each of said character positions, a plurality of groups of cathodes, each such group being associated with one of said anodes and being located in one of said character positions, each of the cathodes having the shape of a segment of one of the characters to be displayed, each of said anodes and its associated cathodes being disposed in an ionizable gas atmosphere at a pressure capable of sustaining cathode glow discharge, a plurality of cathode conductors each electrically connected to one of the cathodes in each character position, a plurality of cathode drivers, each electrically connected to one of said cathode conductors, for energizing said cathodes selectively in response to a first set of input signals, circuit means for selectively energizing said anodes, in synchronism with the selective energization of said cathodes, in response to a second set of input signals, for displaying selected characters in each of said character positions, an auxiliary electrode in the gaseous atmosphere associated with each character position, the current therethrough being a function of the number of cathodes which are glowing, first bias circuit means for maintaining an electrical potential within a predetermined range on said auxiliary electrode, said bias circuit means including a terminal at an initial voltage level electrically connected to said auxiliary electrode and at least one impedance device electrically connected to said terminal, and second bias circuit means for establishing a predetermined bias voltage on said cathodes including a plurality of circuits having bidirectional impedance characteristics, each containing a biasing resistance and being connected from the terminal of the first bias circuit means to a different one of said cathode conductors, and further circuit means connecting each of the cathode drivers and its connected biasing resistance across at least a portion of said impedance device, to reduce the effective impedance connected to said auxiliary electrode as each cathode driver energizes one of said cathodes.

Claim 13

A character display circuit as in claim 9 wherein the plurality of anodes and the plurality of groups of cathodes are all located within a common gas-tight envelope, and wherein the auxiliary electrode is a single electrode associated with all of the character positions and in operative relation to the cathodes and anodes in each such character position.

Claim 14

A character display device as in claim 9 wherein the impedance device comprises a voltage divider having a junction connected to the auxiliary electrode, a predetermined impedance connected from said junction to a first reference potential terminal, and a second predetermined impedance connected from said junction to a second reference potential terminal.

Claim 15

Apparatus for operating multiple-position display devices having a plurality of electrically interconnected groups of cathode elements, an anode associated with each of the cathode groups, and an auxiliary electrode that electrically shields the groups from each other in an ionizable medium, comprising a plurality of cathode drivers having output circuits to be coupled to corresponding ones of the interconnected cathode elemeNts for energizing them selectively in response to a first set of input signals, voltage dividing means coupled between a pair of different reference potential terminals and having a divider junction to be connected to said auxiliary electrode for biasing it at an initial voltage level, the output circuits of the cathode drivers including bidirectional impedance means also coupled to the divider junction, both for pre-biasing the cathode elements from it also and for maintaining the bias voltage on the auxiliary electrode despite changes in the number of cathode elements being driven, to prevent spurious glow in the device irrespective of the display pattern, and means coupled to each of the anodes for energizing them select selectively in response to a second set of input signals synchronous with the first set of input signals.

Claim 16

Apparatus for operating multiple-position display devices having a plurality of electrically interconnected groups of cathode elements, an anode associated with each of the cathode groups, and an auxiliary electrode that electrically shields the groups from each other in an ionizable medium, comprising a plurality of cathode drivers having output circuits to be coupled to corresponding ones of the interconnected cathode elemeNts for energizing them selectively in response to a first set of input signals, voltage dividing means coupled between a pair of different reference potential terminals and having a divider junction to be connected to said auxiliary electrode for biasing it at an initial voltage level, the output circuits of the cathode drivers including bidirectional impedance means also coupled to the divider junction, both for pre-biasing the cathode elements from it also and for maintaining the bias voltage on the auxiliary electrode despite changes in the number of cathode elements being driven, to prevent spurious glow in the device irrespective of the display pattern, and means coupled to each of the anodes for energizing them select selectively in response to a second set of input signals synchronous with the first set of input signals.

Claim 17

The apparatus for operating multiple-position display devices of claim 12 wherein the voltage dividing means comprises series-connected resistances and the cathode driver output circuits include resistance means coupled to the voltage divider junction between the series resistances.

Claim 18

The apparatus defined in claim 20 wherein the means for energizing the anodes includes voltage switching means for each of the anodes coupled for shifting the voltage on them responsive to the second set of input signals in synchronism with the first set of input signals applied to the cathode drivers.

Claim 19

The apparatus characterized by claim 12 further comprising means for blanking the application of the first set of input signals to the cathode drivers for a predetermined interval in advance of signal transition in the second set of input signals.

Claim 20

The apparatus defined in claim 12 further comprising an anode pre-biasing circuit having second voltage dividing means coupled between said pair of reference potential terminals and having a divider junction to which each of the anodes is coupled by impedance means.

Claim 21

The apparatus defined in claim 16 wherein the second voltage dividing means comprises a voltage reference device coupled in series with a resistor and the anodes are coupled to the junction thereof by resistance means.

Claim 22

The apparatus defined in claim 16 wherein the second voltage dividing means comprises series-connected resistances and the anodes are coupled to the divider junction thereof by resistance means between the series resistances.

Claim 23

The apparatus characterized by claim 18 wherein reverse biased unidirectionally conductive means are connected in parallel with the resistance means coupling the anodes to the divider junction of the second voltage dividing means to clamp negative voltage excursions on them.