Protection circuit

Claim 2

In combination with an imaging transducer of the type having an electron beam which is scanned across the face of a target thereof under direction of an applied horizontal deflection rate signal and under direction of an applied vertical deflection signal switchable between different scanning rates, a protection circuit comprising: first means for sensing the absence of said applied horixontal deflection rate signal and for ''''blanking off'''' the electron beam of said imaging transducer in response thereto: second means for sensing the absence of said applied vertical deflection rate signal and for alsO ''''blanking off'''' said electron beam as a response; said first and second means each including a control device which is normally maintained in a first state of conduction by the presence of its associated deflection rate signal but which is rendered to a second state of conduction by the absence of its said associated signal, with the state of conduction of said device at any one time being governed by the energy condition of a charge-discharge circuit further included in each of said first and second means; third means interspersed between each of said first and second means and said imaging transducer for sensing the conductivity state of said control devices and for regulating the bias voltage applied to said transducer to ''''blank'''' or ''''unblank'''' its electron beam as a function thereof and fourth means responsive to the switching of said vertical deflection signal between different scanning rates to vary as a function of the then applied vertical deflection rate, the time for the associated charge-discharge circuit to reach that energy condition at which its control device is rendered to the second state of conduction in the absence of said vertical deflection signal.

Claim 3

The protection circuit of claim 1 wherein said control devices are normally non-conductive, but are rendered conductive in the absence of said deflection rate signals by an increase in energy condition of said charge-discharge circuit beyond a predetermined level.

Claim 4

The protection circuit of claim 2 wherein said control devices are transistors having an input electrode coupled to its associated charge-discharge circuit, a common electrode, and an output electrode at which voltage representations of the conductivity state thereof are developed in accordance with the energy condition of said charge-discharge circuit.

Claim 5

The protection circuit of claim 3 wherein the charge-discharge circuits included within said first and second means each include a capacitor charging to a potential source by means of an included resistor, but wherein the rate of charge for said first means circuit is substantially in excess of the rate of charge for said second means circuit.

Claim 6

In combination with an imaging transducer of the type having an electron beam which is scanned across the face of a target thereof under direction of applied horizontal and vertical deflection rate signals, a protection circuit comprising: first means for sensing the absence of said applied horizontal deflection rate signal and for ''''blanking off'''' the electron beam of said imaging transducer in response thereto; second means for sensing the absence of said applied vertical deflection rate signal and for also ''''blanking off'''' said electron beam as a response; said first and second means each including a control device which is normally maintained in a first state of conduction by the presence of its associated deflection rate signal but which is rendered to a second state of conduction by the absence of its said associated signal, with the state of conduction of said device at any one time being governed by the energy condition of a charge-discharge circuit further included in each of said first and second means; and third means interspersed between each of said first and second means and said imaging transducer for sensing the conductivity state of said control devices and for regulating the bias voltage of said transducer to ''''blank'''' or ''''unblank'''' its electron beam as a function thereof; wherein said control devices are normally non-conductive, but are rendered conductive in the absence of said deflection rate signals by an increase in energy condition of said charge-discharge circuit beyond a predetermined leVel; wherein said control devices are transistors having an input electrode coupled to its associated charge-discharge circuit, a common electrode, and an output electrode at which voltage representations of the conductivity state thereof are developed in accordance with the energy condition of said charge-discharge circuit; wherein the charge-discharge circuits included within said first and second means each include a capacitor charging to a potential source by means of an included resistor, but wherein the rate of charge for said first means is substantially in excess of the rate of charge for said second means circuit; wherein each of said charge-discharge circuits also includes a further normally non-conductive control device which iS rendered conductive by applied horizontal and vertical deflection signals to provide a discharge path for its associated capacitor before the charge thereon increases to the predetermined level at which the change in conductivity from said first state to said second state occurs.

Claim 7

In combination with an imaging transducer of the type having an electron beam which is scanned across the face of a target thereof under direction of applied horizontal and vertical deflection rate signals, a protection circuit comprising: first means for sensing the absence of said applied horizontal deflection rate signal and for ''''blanking off'''' the electron beam of said imaging transducer in response thereto; second means for sensing the absence of said applied vertical deflection rate signal and for also ''''blanking off'''' said electron beam as a response; said first and second means each including a control device which is normally maintained in a first state of conduction by the presence of its associated deflection rate signal but which is rendered to a second state of conduction by the absence of its said associated signal, with the state of conduction of said device at any one time being governed by the energy condition of a charge-discharge circuit further included in each of said first and second means; and third means interspersed between each of said first and second means and said imaging transducer for sensing the conductivity state of said control devices and for regulating the bias voltage of said transducer to ''''blank'''' or ''''unblank'''' its electron beam as a function thereof; wherein said control devices are normally non-conductive, but are rendered conductive in the absence of said deflection rate signals by an increase in energy condition of said charge-discharge circuit beyond a predetermined leVel; wherein said control devices are transistors having an input electrode coupled to its associated charge-discharge circuit, a common electrode, and an output electrode at which voltage representations of the conductivity state thereof are developed in accordance with the energy condition of said charge-discharge circuit; wherein the charge-discharge circuits included within said first and second means each include a capacitor charging to a potential source by means of an included resistor, but wherein the rate of charge for said first means is substantially in excess of the rate of charge for said second means circuit; wherein each of said charge-discharge circuits also includes a further normally non-conductive control device which iS rendered conductive by applied horizontal and vertical deflection signals to provide a discharge path for its associated capacitor before the charge thereon increases to the predetermined level at which the change in conductivity from said first state to said second state occurs.

Claim 8

The protection circuit of claim 5 wherein the charge-discharge circuits of said first and second means each include a time constant network which is selected to respond to the presence of applied horizontal and vertical deflection rate signals to render said further control devices conductive so as to provide a discharge path by which the energy condition of said capacitors can be reduced before said predetermined levels are reached in the ''''blanking'''' of said electron beam.