Visual display apparatus

Claim 2

A visual display apparatus comprising, a gas discharge display tube includinG an extinction voltage measuring electrode and a system of anode and cathode electrodes arranged to define a plurality of discharge gaps within said display tube, a bias control circuit for controlling the supply voltage applied to the electrodes of the gas discharge tube, means for selectively applying the supply voltage to the tube electrodes in a sequence that is independent of the gas discharge condition across the discharge gaps between the tube electrodes, and an extinction voltage measuring circuit coupled to an input of said bias control circuit to provide a reference voltage therefor, said extinction voltage measuring circuit including a capacitor coupled to said extinction voltage measuring electrode so that the measuring electrode is arranged as a recharge electrode for the capacitor.

Claim 3

Visual display apparatus as claimed in claim 1, in which the gas discharge display tube is of a type using a cathode system, an auxiliary anode system and an anode system, cahracterized in that at least the auxiliary anode system is coupled to an output of the bias control circuit.

Claim 4

Visual display apparatus as claimed in claim 1, characterized in that the extinction voltage measuring circuit is coupled to a separate extinction voltage measuring electrode provided in the gas discharge tube and extending substantially throughout the tube.

Claim 5

Visual display apparatus as claimed in claim 1 further comprising a discharge circuit for the capacitor that includes a diode coupling the capacitor to the extinction voltage measuring electrode so that the diode, capacitor and discharge circuit are arranged as a minimum voltage detection circuit.

Claim 6

A visual display apparatus comprising, a gas discharge tube including a system of anode and cathode electrodes arranged to define a plurality of discharge gaps within said display tube and an auxiliary electrode, a bias control circuit for adjusting the value of the supply voltage applied to the electrodes of the display tube as a function of a control signal at the input of the bias control circuit, means for selectively applying the supply voltage to the display tube system of anode and cathode electrodes as a function of the information to be displayed, a reference voltage measuring circuit having an input terminal connected to said auxiliary electrode and an output coupled to the input of the bias control circuit, said measuring circuit including a capacitor coupled to its input terminal and circuit means whereby the value of the display tube extinction voltage acts as a reference voltage for determining the value of the control signal developed at the output of the measuring circuit and hence the value of the supply voltage applied to the tube electrodes.

Claim 7

A visual display apparatus comprising, a gas discharge tube including a system of anode and cathode electrodes arranged to define a plurality of discharge gaps within said display tube and an auxiliary electrode, a bias control circuit for adjusting the value of the supply voltage applied to the electrodes of the display tube as a function of a control signal at the input of the bias control circuit, means for selectively applying the supply voltage to the display tube system of anode and cathode electrodes as a function of the information to be displayed, a reference voltage measuring circuit having an input terminal connected to said auxiliary electrode and an output coupled to the input of the bias control circuit, said measuring circuit including a capacitor coupled to its input terminal and circuit means whereby the value of the display tube extinction voltage acts as a reference voltage for determining the value of the control signal developed at the output of the measuring circuit and hence the value of the supply voltage applied to the tube electrodes.

Claim 8

A visual display apparatus as claimed in claim 5 further comprising a diode connected in circuit to couple the capacitor to said input terminal and polarized to provide a discharge path for the capacitor that includes the auxiliary electrode and at least one cathode electrode of the display tube.

Claim 9

A visual display apparatus as claimed in claim 5 further comprising a diode connected in series with the capacitor to said input terminal and polarized to provide a discharge path for the capacitor that includes the auxiliary electrode and at least one cathode electrode of the display tube, a source of DC voltage, and a charge circuit coupling the capacitor to the DC voltage source.

Claim 10

A visual display apparatus as claimed in claim 5 wherein the display tube includes an auxiliary anode system coupled to an output of the bias control circuit.

Claim 11

A visual display apparatus comprising, a gas discharge tube including a system of anode and cathode electrodes arranged to define a plurality of discharge gaps within said display tube and an auxiliary electrode, a bias control circuit with an output for applying a supply voltage to the anode-cathode electrodes of the display tube and a control input for adjusting the value of the supply voltage as a function of a control siGnal applied thereto, switching means for selectively coupling the output of the bias control circuit to the tube anode-cathode electrodes independent of the discharge state of the electrode discharge gaps, a reference voltage measuring circuit having an input terminal connected to said auxiliary electrode and an output coupled to the control input of the bias control circuit, and said measuring circuit including circuit means for controlling the value of a reference control signal developed at the output of the measuring circuit as a function of the voltage at the tube auxiliary electrode.

Claim 12

A visual display apparatus comprising, a gas discharge tube including a system of anode and cathode electrodes arranged to define a plurality of discharge gaps within said display tube and an auxiliary electrode, a bias control circuit with an output for applying a supply voltage to the anode-cathode electrodes of the display tube and a control input for adjusting the value of the supply voltage as a function of a control siGnal applied thereto, switching means for selectively coupling the output of the bias control circuit to the tube anode-cathode electrodes independent of the discharge state of the electrode discharge gaps, a reference voltage measuring circuit having an input terminal connected to said auxiliary electrode and an output coupled to the control input of the bias control circuit, and said measuring circuit including circuit means for controlling the value of a reference control signal developed at the output of the measuring circuit as a function of the voltage at the tube auxiliary electrode.

Claim 13

A visual display apparatus as claimed in claim 9 wherein said measuring circuit means includes a capacitor coupled to its input terminal.

Claim 14

A visual display apparatus as claimed in claim 9 wherein said circuit means includes a capacitor and diode connected in series to said measuring circuit input terminal.

Claim 15

A visual display apparatus as claimed in claim 15 wherein said circuit means further comprises a voltage breakdown element coupled between the junction of the capacitor and diode and the output of the measuring circuit.

Claim 16

A visual display apparatus as claimed in claim 10 wherein said display tube includes an auxiliary anode system and said bias control circuit includes a second output coupled to said auxiliary anode system for applying a supply voltage thereto determined by the control signal at the input of the bias control circuit.

Claim 17

A visual display apparatus as claimed in claim 9 wherein said display tube includes a single anode and a plurality of cathodes arranged to define said plurality of discharge gaps within the display tube.