Abstract:
The invention describes a turn-on delay device ( 10 ) for a visual display unit ( 14 ) which can be placed into an idle state by disabling at least one signal (H-SYNC IN, V-SYNC IN) controlling the visual display unit ( 14 ). The turn-on delay device contains, amongst other things, a disabling device ( 42, 44, 46 ) which disables the signal (H-SYNC IN, V-SYNC IN) for a predetermined delay period. When the delay period has elapsed, the signal (H-SYNC IN, V-SYNC IN) is supplied to the visual display unit ( 14 ).

Description:
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&#39;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&#39;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&#39;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&#39;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&#39;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&#39;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 using a potentiometer. 
     If a voltage supply fed by the horizontal sync signal is provided in the turn-on delay device, then there is no need for an external voltage supply or for a voltage supply in the form of a battery. This reduces production and operating costs and makes it easier for existing computer systems with the turn-on delay device to have additional equipment fitted. 
     To reduce the space requirement of the turn-on delay device, it can be produced using surface mount technology, also called SMD technology. 
     According to a further aspect of the invention, a method of deactivating a visual display unit is specified. 
     Further advantageous developments of the invention are dealt with in the subclaims and in the description which follows: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in more detail below with the aid of the figures, in which: 
     FIG. 1 shows a schematic illustration of a system comprising a computer, a turn-on delay device and a visual display unit, and 
     FIG. 2 shows a circuit arrangement for the turn-on delay device shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The basic way in which the invention works is illustrated in FIG. 1, which shows a turn-on delay device  10  connecting a computer  12  to a visual display unit  14 . The components shown in FIG. 1 can be part of a system used in a bank, for example, to allow a customer of the bank to perform cash transfers or account debits automatically. 
     The design of the computer  12  and of the visual display unit  14  and the way in which they work are known per se, so that the description of these components can be kept brief at this point. 
     The computer  12  can be a personal computer of known type having an interface  16  for connecting the visual display unit  14 . The computer  12  also contains a controller  18 , for example in the form of a plug-in graphics card, which conditions the textual and graphics information processed in the computer for the visual display unit  14 . In the illustrative embodiment to be explained, the controller  18  is a VGA graphics card which converts the textual and graphics information into an analog signal and supplies it to the visual display unit  14 , which, for its part, operates on the basis of the VGA standard. 
     The visual display unit  14  contains a screen  20  having an integrated input device  21 , also called a touchscreen, which a customer of the bank can use to make entries by touching the screen  20 . The visual display unit  14  also has an input controller  22 , i.e. a touch controller, for driving the touchscreen, and a voltage supply  22 . 
     In known systems, a connecting cable  26  coming from the visual display unit  14  is connected directly to the interface  16  of the computer  12 . The connection between the connecting cable  26  and the interface  16  is usually made using a standardized plug-in connection. Thus, for example, the connecting cable  26  is provided with a conventional 15-pin D-subminiature connector  28  which, in a system based on the prior art, is plugged into a corresponding connector receptacle  30  on the interface  16  of the computer  12 . 
     The system shown in FIG. 1 is distinguished from the prior art by the turn-on delay device  10 , which is connected between the computer  12  and the visual display unit  14 . On the turn-on delay device  10 , there is a connector receptacle  32  which matches the D-subminiature connector  28  on the connecting cable  26  and can be identical to the connector receptacle  30  on the interface  16  of the computer  12 . The D-subminiature connector  28  on the connecting cable  26  is plugged into the connector receptacle  32  on the turn-on delay device  10 . In place of the connecting cable  26  from the visual display unit  14 , a connecting cable  34  is connected to the connector receptacle  30  on the interface  16  using a D-subminiature connector  36 . The connecting cable  34  can be permanently attached to a housing of the turn-on delay device  10 . 
     The VGA graphics card  18  produces a plurality of control signals which are necessary for showing an image in the visual display unit  14  and of which FIG. 1 shows only a horizontal sync signal H-SYNC IN and a vertical sync signal V-SYNC IN. The sync signals H-SYNC IN, V-SYNC IN are supplied via the connecting cable  34  to the turn-on delay device  10 , are disabled there (as is yet to be described) for a predetermined delay time in the starting phase of the computer, and are switched through to the visual display unit  14  when this delay time has elapsed. In FIG. 1, the switched-through sync signals are called H-SYNC OUT and V-SYNC OUT. The sync signals H-SYNC OUT and V-SYNC OUT coordinate the movement of an electron beam in a picture tube (not shown in FIG. 1) in the visual display unit  14 . 
     The visual display unit  14  has an energy-saving function as provided nowadays in VGA monitors. If the visual display unit  14  registers the absence of the sync signals H-SYNC OUT and V-SYNC OUT, it is placed in an idle state, where, by way of example, its screen  20  goes blank. The technical precautions necessary for this purpose on the visual display unit  14  are known per se and are therefore not explained further at this point. The essential thing is that the visual display unit  14  reacts, in the manner just described, to the absence of the sync signals H-SYNC OUT and V-SYNC OUT. 
     FIG. 2 shows a possible circuit arrangement for the turn-on delay device  10 , which switches through the sync signals H-SYNC IN and V-SYNC IN produced by the controller  18  to the visual display unit  14  when a settable disabled time has elapsed after the computer  12  has been turned on or restarted. The circuit arrangement shown in FIG. 2 contains a functional unit which builds up the voltage supply for the turn-on delay device  10  in a manner which is yet to be described. This functional unit comprises the resistors R 1 , R 2 , R 3 , R 7 , the diodes D 1 , D 2 , D 3 , the capacitors C 1 , C 2 , C 3 , and the switch  40 . A timing circuit  42  forms a further functional unit with the resistors R 4 , R 6 , the potentiometer R 5  and the capacitors C 4  and C 5 . In the illustrative embodiment being explained, the timing circuit  42  is an ICM7555IBA-type integrated circuit, operated as a monostable multivibrator. The other components shown in FIG.  2  and connected to the timing circuit  42  are the resistors R 8 , R 9 , R 10 , the capacitor C 6  and the switches  44 ,  46  and  48 . These components can also be essentially regarded as a functional unit. 
     The switch  40  and further switches  44 ,  46 ,  48  are combined in a quad switch  50 . The quad switch  50  is produced in CMOS technology and is in the form of an HEF4066BT-type integrated circuit. The circuit arrangement shown in FIG. 2 also contains inputs  52 ,  54 ,  56  and outputs  58 ,  60 ,  62 . The inputs  52 ,  54 ,  56  are to be allocated to the connector receptacle  30  and the outputs  58 ,  60 ,  62  are to be allocated to the D-subminiature connector  28  shown in FIG.  1 . 
     The sync signals H-SYNC IN, V-SYNC IN produced by the VGA graphics card  18  are supplied to the turn-on delay device  10  via the inputs  52  and  54 , respectively. The input  56  and the output  62  of the turn-on delay device  10  are grounded (GND). 
     The way in which the circuit arrangement shown in FIG. 2 works is explained below. In the phase in which the graphics card  18  is still not producing any sync signals H-SYNC IN and V-SYNC IN, there is no signal present at the inputs  52  and  54  of the turn-on delay device  10 . The switches  44 ,  46  of the integrated circuit  50  are off at this instant. When the sync signals H-SYNC IN and V-SYNC IN appear at the inputs  52 ,  54 , the voltage supply is built up in the turn-on delay device  10  by utilizing the energy supplied to the turn-on delay device  10  in the form of the sync signal H-SYNC IN. For this purpose, the sync signal H-SYNC IN is supplied to the functional unit mentioned initially, which comprises resistors R 1 , R 2 , R 3 , the diodes D 1 , D 2 , D 3  and the capacitors C 1 , C 2 , C 3 , as well as the switch  40  with the resistor R 7  connected upstream of it. The resistors R 1 , R 2 , R 3 , R 7  are used for current limiting, and the diodes D 1 , D 2  and D 3  produce smoothed DC voltages from the sync signal H-SYNC IN, which is an AC voltage signal, in combination with the capacitors C 1 , C 2 , C 3 . If the voltage at an input  64  of the switch  40  reaches a predetermined value, the switch  40  turns on, and the voltage supply is built up. Since the voltage required for operating the turn-on delay device  10  is provided by the sync signals H-SYNC IN and V-SYNC IN, there is no need for an external voltage supply or for a voltage supply in the form of a battery. 
     When the voltage supply has been produced in the turn-on delay device  10  in the manner just described, the timing circuit  42  operated as a monostable multivibrator is started via an input  2  which has an RC combination comprising the resistor R 6  and the capacitor C 5  connected upstream of it. At this moment, an output  3  of the timing circuit  42  is changed to an unstable state, which continues for a predetermined delay time. In this phase, the duration of which is defined by the resistor R 4 , the capacitor C 4  and the potentiometer R 5 , the switches  44 ,  46  remain off. When the delay time has elapsed, the output  3  of the timing circuit  42  reverts to a stable state and turns on the switches  44 ,  46  in the integrated circuit  50  via the resistors R 8 , R 9 , R 10 , the capacitor C 6  and the switch  48 . The sync signals H-SYNC IN and V-SYNC IN are now switched through to the outputs  58  and  60  of the turn-on delay device  10  by the switches  44 ,  46  and are thus available to the visual display unit  14 . The switched-through sync signals are called H-SYNC OUT and V-SYNC OUT in FIG.  2 . The setup of the screen can finally be completed in the visual display unit  14  using the sync signals H-SYNC OUT and V-SYNC OUT. 
     The delay time after which the timing circuit  42  operated as a monostable multivibrator turns on the switches  44 ,  46  via its output  3  is equivalent to the disabled time, in which the screen  20  of the visual display unit  14  goes blank after the operating system of the computer  10  is started. This delay time can be set at the potentiometer R 5 , whose resistance value can be set externally using a screwdriver, for example. In the illustrative embodiment shown in FIG. 2, the delay time can be set to a value between 0.5 and 5 minutes. 
     The invention is not restricted to the circuit arrangement shown in FIG. 2, which should merely be regarded as a specific illustrative embodiment. The dimensional design of the components used in the circuit arrangement shown in FIG. 2 is suited to the sync signals H-SYNC IN and V-SYNC IN as produced by the VGA graphics card  18 . For the illustrative embodiment shown in FIG. 2, the components have the following dimensions: 
     R 1 =680, R 2 =1.8 k, R 3  22=k, R 4 =22 k, R 5  to 1 M, R 6 =1 M, R 7 =100 k, R 8 =1 M, R=100 k, R 10 =1.8 k, C 1 :1 F/16 V, C 2 :10 F/16 V, C 3 :1 F/16 V, C 4 :100 F/10 V, C 5 :100 nF/50 V, C 6 :100 nF/50 V. 
     The capacitors C 2  and C 4  are electrolytic capacitors having the polarity indicated in FIG.  2 . The diodes D 1  and D 2  used are BAR43S-type diodes and the diode D 3  used is a BAR42-type diode. 
     List of Reference Symbols 
       10  Turn-on delay device 
       12  Computer 
       14  Visual display unit 
       16  Interface 
       18  Controller 
       20 ,  21  Screen with integrated input device 
       22  Input controller 
       24  Voltage supply for the visual display unit 
       26  Connecting cable 
       28  D-subminiature connector 
       30  Connector receptacle 
       32  Connector receptacle 
       34  Connecting cable 
       36  D-subminiature connector 
       40  Switch 
       42  Timing circuit 
       44  Switch 
       46  Switch 
       48  Switch 
       50  Quad switch 
       52  Input 
       54  Input 
       56  Input 
       58  Output 
       60  Output 
       62  Output 
     R 1  to R 10  Resistors 
     C 1  to C 6  Capacitors 
     D 1 , D 2 , D 3  Diodes