Circuit for operating multiple position display tubes

Claim 2

Apparatus for operating multiple-position display devices having a plurality of interconnected groups of cathode elements, an anode associated with each of the groups and an auxiliary electrode that is common to all of the groups and shields them from each other comprising a plurality of drivers having their output terminals 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 reference terminals and having a divider junction, means coupled to each of the anodes for energizing them selectively in response to a second set of input signals, and being biased in common with the voltage dividing means from one of said reference terminals, the auxiliary electrode being coupled to the divider junction to be biased at a level that is directly proportional to the anode biasing potential for preventing spurious glow in the device irrespective of variations in the bias potential available for the device.

Claim 3

The apparatus for operating multiple-position display devices of claim 1 wherein the cathode drivers are also coupled to the divider junction so that the impedance of a portion of the divider will vary as an inverse function of the number of cathode elements that are being driven, to prevent spurious glow in the device irrespective of the display pattern.

Claim 4

The apparatus for operating multiple-position display devices of claim 2 wherein the output circuits of the cathode drivers are each coupled to the divider junction by impedance means and appear in electrical parallel with a portion of the divider when the cathode drivers are activated.

Claim 5

The apparatus defined in claim 3 wherein the voltage dividing means comprises a resistive voltage divider and the cathode driver output terminals are each coupled to the voltage divider junction by resistance means.

Claim 6

The apparatus for operating multiple-position display devices of claim 2 wherein the cathode drivers are each coupled in electrical parallel with a portion of the voltage dividing means.

Claim 7

The apparatus defined in claim 5 wherein the voltage dividing means comprises a resistive voltage divider and the cathode driver output terminals are each coupled to the voltage divider junction by resistance means.

Claim 8

The apparatus for operating multiple-position display devices of claim 1 wherein the means for energizing the anodes includes a driver for each of the anodes coupled for driving them responsive to the second set of input signals and in synchronism with the first set of input signals applied to the cathode drivers.

Claim 9

The apparatus defined in claim 7 further comprising a voltage reference device connected in series with an impedance means between a pair of reference terminals and the anodes each being coupled to the junction of them by reverse-biased assymetrically conductive means.

Claim 10

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 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, the current through said auxiliary electrode being a function of the number of cathodes which are glowing, and bias circuit means for biasing said auxiliary electrode to a voltage intermediate the operating voltage of said anode and said cathodes, said bias circuit means including 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 and serving to change the level of the impedance connected to said auxiliary electrode as each cathode driver is energized.

Claim 11

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 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, the current through said auxiliary electrode being a function of the number of cathodes which are glowing, and bias circuit means for biasing said auxiliary electrode to a voltage intermediate the operating voltage of said anode and said cathodes, said bias circuit means including 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 and serving to change the level of the impedance connected to said auxiliary electrode as each cathode driver is energized.

Claim 12

A character display circuit as in claim 9 wherein said current passes from the anode through the ionizable gas to the auxiliary electrode, and at least a portion of said current flow 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 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 13

A character display circuit as in claim 9 wherein the cathode drivers are transistors, and wherein the means for selectively energizing said cathode drivers comprises circuit means connected to the transistors to render them more conductive in response to input signals, and wherein the transistors are all connected across at least a portion of the impedance device to reduce the effective impedance connected to said auxiliary electrode for each transistor that is energized.

Claim 14

A character display circuit as in claim 9 further including a plurality of additional impedance devices, one connected in series with each of said current drivers and the series circuit is connected across at least a portion of the first-mentioned impedance device, and wherein the current drivers are rendered conductive when energized, so that as each driver is energized its associated additional impedance device is effectively connected across the first-mentioned impedance device.

Claim 15

A character display circuit 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 16

A character display circuit as in claim 5 wherein each cathode driver is connected in series with an additional impedance driver, and each such series is connected from said junction to one of said reference potential terminals.

Claim 17

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 the gaseous atmosphere in operative relation to the auxiliary electrode, 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 cathode to cause it to glow in response to an input signal, and bias circuit means for biasing said auxiliary electrode to a voltage intermediate the operating voltage of said anode and said cathodes, said bias circuit means including at least one impedance device connected electrically to said auxiliary electrode, the current through the auxiliary electrode to said impedance device being a function of the number of cathodes which are glowing, and said cathode drivers being connected electrically across at least a portion of said impedance device to modify the effective impedance connected to said auxiliary electrode as each of the cathode drivers responds to an input signal to cause its connected cathode to glow, so as to compensate at least in part for any voltage change which the increased current through the auxiliary electrode tends to produce as an increased number of cathodes glow.

Claim 18

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 the gaseous atmosphere in operative relation to the auxiliary electrode, 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 cathode to cause it to glow in response to an input signal, and bias circuit means for biasing said auxiliary electrode to a voltage intermediate the operating voltage of said anode and said cathodes, said bias circuit means including at least one impedance device connected electrically to said auxiliary electrode, the current through the auxiliary electrode to said impedance device being a function of the number of cathodes which are glowing, and said cathode drivers being connected electrically across at least a portion of said impedance device to modify the effective impedance connected to said auxiliary electrode as each of the cathode drivers responds to an input signal to cause its connected cathode to glow, so as to compensate at least in part for any voltage change which the increased current through the auxiliary electrode tends to produce as an increased number of cathodes glow.

Claim 19

A voltage compensation circuit as in claim 15 wherein the impedance device comprises a voltage divider having a junction connected to the auxiliary electrode, a first 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 20

A voltage compensation circuit as in claim 16 further including a plurality of resistors, one connected in series with each of said cathode drivers, and wherein said cathode drivers are transistors, so that a plurality of resistor-transistor series circuits are connected from said junction to one of said reference potential terminals, and wherein as each transistor is energized it causes its connected cathode to glow and its series-connected resistor to be effectively connected across one of said predetermined impedances.

Claim 21

A voltage compensation circuit as in claim 17 wherein said first and second predetermined impedances are first and second resistors.

Claim 22

A voltage compensation circuit as in claim 15 further including an anode voltage source terminal and circuit means for connecting said terminal to said anode, a cathode voltage source terminal, with the cathode drivers being connected between the respective cathodes and said cathode voltage source 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 source terminal, and a second predetermined impedance connected from said junction to said cathode voltage source terminal.

Claim 23

A character display circuit for displaying any one of a plurality of 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 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 envelope having an ionizable gas atmosphere capable of sustaining cathode glow, a plurality of cathode conductors each electrically connected to one of the cathodes in each character position, a plurality of cathode drivers, each 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 flow therethrough being a function of the number of cathodes which are glowing, and bias circuit means for maintaining an electrical potential within a predetermined range on said auxiliary electrode, irrespective of the number of cathodes glowing, said bias circuit means including at least one impedance device in series with said auxiliary electrode, a plurality of resistors, each of which is connected to one of said cathode drivers, and circuit means connecting each said cathode driver and connected resistor across at least a portion of said impedance device, so as to reduce the effective impedance coNnected to said auxiliary electrode as each such cathode driver energizes one of said cathodes.

Claim 24

A character display circuit for displaying any one of a plurality of 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 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 envelope having an ionizable gas atmosphere capable of sustaining cathode glow, a plurality of cathode conductors each electrically connected to one of the cathodes in each character position, a plurality of cathode drivers, each 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 flow therethrough being a function of the number of cathodes which are glowing, and bias circuit means for maintaining an electrical potential within a predetermined range on said auxiliary electrode, irrespective of the number of cathodes glowing, said bias circuit means including at least one impedance device in series with said auxiliary electrode, a plurality of resistors, each of which is connected to one of said cathode drivers, and circuit means connecting each said cathode driver and connected resistor across at least a portion of said impedance device, so as to reduce the effective impedance coNnected to said auxiliary electrode as each such cathode driver energizes one of said cathodes.

Claim 25

A character display circuit as in claim 20 wherein the auxiliary electrode contains a portion extending between the anode and cathodes of each character position and those of the next adjacent character position, to electrically isolate the electrodes of the respective character positions from each other.