On delay device for a visual display unit

Communications: electrical – Visual indication

Reexamination Certificate

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Details

C340S010600

Reexamination Certificate

active

06239717

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a turn-on delay device for a visual display unit.
In many areas of public life, for example in the services sector, computer systems are today used which allow a user to perform transactions automatically without having to rely on external assistance. An example of this is cash dispensing machines at banks, which can be used by a customer of the bank to withdraw money from his account even outside business hours. Such computer systems usually contain a central computer to which an input device and a visual display unit, i.e. a monitor, as an output device, are connected. The user uses the input device to supply the necessary input information to the computer system. The input device used can be a keyboard or a so-called touchscreen, for example. A touchscreen is understood as being an input device which is integrated into the screen of the visual display unit and converts touches from the user into input information.
The visual display units used today are generally monitors operating on the basis of the so-called VGA standard, which condition an analog signal containing textual and graphics information and display the corresponding images on their screen. The analog signal is produced in the computer by a control device which is tuned to the visual display unit used. A control device tuned to a VGA monitor is also called a VGA graphics card.
A computer system operated in the manner just described needs, like any other computer system, to be restarted from time to time when it has been turned off for maintenance work, for example, or when its voltage supply has been interrupted for other reasons. When the computer is started, i.e. when an operating system is loaded into the computer's main memory, system messages are generally displayed on the screen of the visual display unit. No entries must be made using the input device in this phase, since an error causing the computer system to fail completely will otherwise be produced in the computer system. Such system failure is also called a “system crash”.
Cash dispensing machines now frequently encounter the problem that a user misinterprets the system messages displayed on the screen of the visual display unit and makes entries in the computer system's starting phase, for example by touching the touchscreen, which causes the system crash just described. Such a system failure generally needs to be put right by a technician, which means that the cash dispensing machine is out of service for a relatively long time.
A known solution to the problem just described is to turn off the voltage supply of the visual display unit in the starting phase of the computer system, with the result that the system messages do not appear on the screen in this phase and the user does not feel encouraged to actuate the input device. If a touchscreen is used as the input device, this solution is not practical, however, since the touchscreen and the input controller driving it, which is also called a touch controller, is supplied with voltage by the voltage supply for the visual display unit. When the visual display unit is turned off, communication between the computer's operating system and the input controller is thus interrupted, which means that the input controller, and hence the touchscreen, are not operational when the visual display unit has been turned on.
SUMMARY OF THE INVENTION
EP-A0 678 843 discloses a method of deactivating a visual display unit in which the visual display unit can be placed into the idle state by disabling at least one signal controlling said visual display unit, the signal produced by a control device being disabled for a predetermined delay period.
The object of the invention is to specify a device which can minimize the risk of a user who is misguided by the computer system's system messages causing the computer system to fail.
The invention achieves this object with a turn-on delay device for a visual display unit which can be placed in an idle state by disabling at least one signal controlling the visual display unit. The turn-on delay device contains at least one input which is connected to a control device supplying the signal to it, a disabling device which disables the signal for a predetermined delay time, and at least one output which is connected to the visual display unit and supplies the signal to the latter when the delay time has elapsed.
Modern visual display units generally have a so-called energy-saving function which ensures that the visual display units go blank if one or more control signals are absent. Functioning as control signals are usually a horizontal sync signal and a vertical sync signal, which are produced by a control device in a computer, e.g. a graphics card, and coordinate the movement of an electron beam in the visual display unit's picture tube, with the horizontal sync signal controlling the horizontal flyback and the vertical signal controlling the vertical flyback of the electron beam as the screen is set up. It is now a provision of the invention that, connected between the computer's control device and the visual display unit, there is a turn-on delay device which blocks the control signals for a predetermined delay time when the computer is started, so that the screen of the visual display unit is blank while the operating system is loaded, and the system messages which are otherwise displayed on the screen are not displayed. In this way, it is possible to minimize the risk of a user standing in front of the visual display unit feeling prompted by the system messages displayed on the screen to make entries using an input device, for example a keyboard or a touchscreen, and thus causing the computer system to fail completely.
The invention makes it possible to add further equipment to an existing computer system in the manner shown above irrespective of the operating system and of the software used, without needing to make any considerable changes to the computer system. The invention can, in particular, be applied to all computer systems in which a control device operating on the basis of the VGA standard, i.e. a VGA graphics card, drives a VGA monitor. The connection between the turn-on delay device and the computer, on the one hand, and between the turn-on delay device and the visual display unit, on the other hand, can be made using standard connections, such as D-subminiature plug-ins connections and corresponding connector receptacles. In one advantageous development of the invention, the disabling device contains at least two switches, of which a first switch connects a first input, to which the control device supplies a horizontal sync signal, to a first output, and a second switch connects a second input, to which the control device supplies a vertical sync signal, to a second output. The mutually associated inputs and outputs are accordingly connected to one another directly via a respective switch driven by the disabling device. Advantageously, the switches can be in the form of CMOS switches. Advantages of the switches produced in CMOS technology are low susceptibility to interference, low space requirement and high temperature stability.
The disabling device can also contain a timing circuit which turns on the first and the second switch when the delay time has elapsed. Inexpensive integrated circuits can be used as the timing circuit.
The timing circuit is particularly simple to produce using a monostable multivibrator. When the computer system is started, the sync signals supplied to the delay device can switch (as an example) an output, driving the switches, of the multivibrator to its unstable state. In this state, the output of the multivibrator causes the switches to be off and thus causes the sync signals to be disabled. When the delay time has elapsed, the output of the multivibrator automatically reverts to its stable state and turns on the switches. The sync signals are now available to the visual display unit for setting up the screen. The delay time can advantageously be set us

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