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1. WO1988004095 - SYSTEME DE COMMANDE A UTILISER AVEC DES ENREGISTREURS DE CASSETTES VIDEO

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

"CONTROL SYSTEM FOR USE WITH VIDEO CASSETTE RECORDERS"

THIS INVENTION relates to a control system to be used in association with a video cassette recorder means and an in-house video system which can be formed therefrom. Moreover the invention particularly relates to a control system for controlling the sequential operation of a video cassette recorder means and a video generating source means so as to enable a video signal generated from the video generating source means to be displayed on a display medium subsequent to the display of a video signal generated from the video cassette recorder means on the display medium after the cessation of the display of the first video signal.

The invention has particular application in the operation of in-house video screenings on a television receiver where a video tape is screened by a video cassette recorder at prescribed times of the day and computer generated graphics is screened by a computer during the intervening periods.

In the specification a video cassette recorder means is defined to include a video cassette recorder which performs a plurality control functions for controlling the operation of a video cassette tape to be screened on a display medium, such as play, stop, rewind or combinations of these such as stop/rewind. In addition, a video generating source means is defined to include any apparatus which is capable of generating a video signal to be displayed on a display medium. A video cassette recorder means shall hereinafter be referred to as a 'VCR means' and a video generation source means shall hereinafter be referred to as a 'VGS means'.

In accordance with one aspect of the present invention, there is provided a control system for controlling the sequential operation of a VCR means having a plurality of control functions and a VGS means so as to enable a video signal generated from said VGS means to be displayed on a display medium subsequent to the display of a video signal generated from said VCR means on said display medium, comprising:- detecting means for detecting the presence or absence of a video signal generated from said VCR means and generating an active signal in response to detecting the absence of said video signal on said display medium;
timing means for timing out a predetermined time period in response to the generation of said active signal; and
actuating means for actuating the stop and rewind controls of said VCR means whilst in the play mode and initiating operation of said VGS means to display the video signal thereof on said display medium, only after said timing means times out said predetermined time period and said active signal is still present.

Preferably, a control means as claimed at claim 1. wherein said actuating means includes logic to generate a control signal only if said active signal is present when said timing means times out predetermined delay period, said control signal being provided to both actuate the stop and rewind controls of said VCR means when in the play mode and initiate operation of said VGS means to display said video signal thereof.

Preferably, a control system as claimed at claim 1 or 2 , wherein said control system includes resetting means to reset said detecting means after the elapsing of a further predetermined time period from the time of generation of said reference signal.

Preferably, said actuating means maintains isolation from the controls of said VCR means during operation thereof.

In accordance with another aspect of the present invention, there is provided an in-house video system comprising:- a VGS means for generating a video signal;
a plurality of VCR means each for generating a dedicated video signal derived from a video cassette tape played thereon;
a display medium for sequentially displaying said video signals such that at most only one video signal generated from said VGS means or VCR means is displayed at any one time; and
a control system as claimed at any of the preceding claims.

The invention will be better understood in the light of the following description of one specific embodiment thereof. The description is made with reference to the accompanying drawings , wherein : -

Fig. 1 is a block diagram showing the location of the control system with respect to a series of VCRs and a computer;

Fig. 2 is a circuit diagram showing the electronic configuration of the control system; and

Fig. 3 is a timing diagram relating to the circuit shown at Fig. 2.

As shown at Fig. 1, the embodiment is directed towards an in-house video system 11 which generally comprises VCR means in the form of three VCRs 13 having their respective video output ports 14 connected to a common transmission output line 15 for transmission of video signals derived therefrom to a common receiver input line 16 connected to a display medium such as a plurality of television receivers 17. In addition to the VCRs 13, a VGS means in the form of a computer 19 has its graphic output line 21 also connected to the common transmission line 15. In such an arrangement, the VCRs 13 are operated under the control of the computer 19 via a control system 23 which provides an interface between the VCRs and the computer . The computer 19 is connected to the control system 23 by virtue of bidirectional communication lines 24 and the VCRs 13 are connected to the control system 23 by virtue of a plurality of control lines 26.

In the preferred form of operation of the system, each of the VCRs 13 is provided with its own video tape. Two of the tapes may depict separate movies and the third a prelude used in conjunction with each movie. For example, the first VCR 13a may play a tape depicting a second movie.

The computer 19 via the control system 23 may oversee the operation of the VCRs in conjunction with a real time clock and a program which initiates the operation of selected VCRs. Thus, the computer may start the operation of the first VCR 13a so as to play the prelude video tape at a prescribed time for display on the receivers 17 and automatically start the operation of the second VCR 13b at the end of the prelude so that the first movie may subsequently be screened on the receivers. At the conclusion of the screening of the first movie, the computer may automatically enter a graphics generating mode so that graphics can be displayed upon the television receivers via the graphic output line 21. Computer generated graphics may subsequently be displayed until, at a later prescribed time, the computer determines the start of the first VCR 13a once again followed by the automatic operation of the third VCR 13c, so that the second movie may be screened on the receivers 17. This cycle of operation may be continued throughout the day with the prelude and appropriate movie being screened at selected times of the day which have been programmed into the computer.

The computer 19 is connected to the control system 23 via lines 24 to detect the occurrence of this controlling operation of the system in response to detecting the absence of video signals at the common transmission line 15, and effect either the output of computer generated graphics therefrom via video output line 21 for display, or the start of another VCR, 13b or 13c to screen the video tape thereof for display, as determined by the control program of the computer.

Prior to the start of the second or third VCR, however, it is necessary to stop the operation of the first VCR 13a to enable the next VCR to transmit its output video signal on the common transmission output line 15. In addition, it is preferable to rewind the prelude tape of the first VCR back to start, ready for operation when it is desired to screen the other movie later in the day.

The control system 23 is provided to facilitate the controlling function of the computer 19 on the VCRs 13 whilst maintaining isolation between the computer and the VCRs. In order to appreciate the operation of the control system 23 the means by which the control functions of the VCRs are performed shall now be described.

In certain types of VCR, the stop, start and rewind functions together with several other functions are actually controlled by an on-board microprocessor which continually scans a series of sensors to determine a particular function to be performed by the VCR. These sensors are connected in circuit with a series of corresponding switches which can be individually operated to close or open the circuit associated therewith and hence alter a voltage or current parameter sensed by the corresponding sensor. The sensors may be sensitive to changes in potential or current with respect to time provided by energising passive networks of the resistor-capacitor (RC) type which are arranged to uniquely specify a particular control function which is to be performed. For example, it may be necessary to provide a voltage at a prescribed potential of say 5 volts for a period of ten milliseconds to an appropriate sensor for the microprocessor to enact a stop control followed by a rewind control. Alternatively, it may be necessary to provide a voltage of 2 volts for a period of 2 milliseconds to a sensor for the microprocessor to enact a start control function. The switches associated with each sensor can be operated directly either by manual control or automatic control.

In the case of manual control, there is usually provided a button or knob on the outer control panel of the VCR which may be depressed or turned to initiate a desired control function. This depressing of the button or turning of the knob causes a switch associated therewith to close the circuit in which it is connected and hence provide the appropriate parameter for sensing by the corresponding sensor connected thereto. When it is desired to terminate the control function, further depression of the button or return of the knob causes the switch to open the circuit and so remove the parameter from the sensor.

In the case of automatic control, a relay may be used to directly open or close the switch in the circuit and so provide or remove the appropriate parameter to the sensor.

In the present embodiment, the control system 23 utilises these facilities by opening and closing an appropriate relay connected into a particular circuit to remove or provide the desired parameter to a sensor to achieve the desired control function. Moreover, the control system 23 energises or de-energises the relay, wired in series with a circuit, such that when the relay is energised, the contact arm is pulled in and the circuit is closed to effect the desired control function, and when the relay is de-energised the contact arm is released and the circuit is opened to cease the control function. Accordingly, the control system 23 is connected to a series of relays 25 which are individually wired into series with sensor circuits of each of the VCRs 13.

With reference to Figures 2 and 3 of the drawings, the control system 23 essentially comprises a detecting means 27, a timing means 29 and an actuating means 31. The detecting means 27 derives its input via a video input line 35 connected to the common transmission line 15, so as to detect the presence or absence of video signals thereon and generates an active signal in response to the latter which is received by the timing means 29 and actuating means 31.

The detecting means comprises a video amplifier 33 which is adapted to receive a video input signal from the video input line 35, a digital switching transistor 37 connected to the output 39 of the video amplifier 33, a filter 41 connected to the output 43 of the digital transistor 37, and a comparator 45 connected to the output 47 of the filter.

The video amplifier 33 is coupled to the video input line 35 and the input of the digital transistor 37 by means of coupling capacitors C1 and C2 respectively, so as to provide an input signal to the digital transistor 37 in response to detecting video signals at input lien 35, at a level which may cause switching thereof. The digital transistor 37 consequently produces a series of pulses at its output line 43 in response to the receipt of input signals from the video amplifier 33. Furthermore, the digital transistor 37 is configured to produce a DC high level signal in response to the absence of video signals received at the input lien 35 of the video amplifier and a DC low level signal in response to the presence of video signals.

The filter 41 is of the low pass RC type and is provided to smooth the leading and trailing edges of the pulses produced by the digital transistor 37, effectively providing a slight delay on the application of changes in signal level at the output A of the filter, which is in turn applied to the input of the comparator 45.

The comparator 45 is configured such that the non-inverting input thereof is connected to the wiper arm of a reference potentiometer 49 and the inverting input thereof is connected to the output A of the filter 41. Consequently, the output B of the comparator 45 provides a high level signal in instances where the output potential of the filter is less than the reference potential and produces a low lever output when the converse situation applies. The wiper arm of the potentiometer 49 is set such that when no video is detected at the input 35, i.e. when the output of the digital transistor 37 is high, the potential at the inverting input of the comparator 45 exceeds the potential at the non-inverting input thereof, and when a video signal is detected at the input 35, i.e.

when the digital transistor output is low, the potential of the inverting input of the comparator drops below the reference potential. Therefore, a high level signal at the output B of the comparator indicates that video is present at the input line 35, and a low level signal indicates that video is not present at the input line 35. This low level signal for the purposes of the present embodiment, corresponds to the generation of the active signal.

To illustrate the above more clearly, reference should be made to the timing diagram at Fig. 3 of the drawings showing the voltage wave forms at points A and B of the circuit, wherein the delaying effect of the filter 41 is shown in substantially smoothing out the leading edge of the wave form produced at A upon detecting no video at the input 35.

The timing means 29 essentially consists of a monostable multi-vibrator 51 coupled to the output 3 of the comparator 45 of the detecting means, by means of a coupling capacitor C3. The monostable 51 is triggered in response to a negative going pulse which is produced by virtue of the capacitor C3 at the output B of the comparator 45, in response to the output signal of the comparator going low i.e. in response to an active signal indicating the detection of no video signal at the input 35. This signal is applied to the input C of the monostable and triggers the monostable 51 to produce a high signal at its output D of a time period determined by the setting of the RC network 53 of the monostable. The output D of the monostable 51, which forms the output of the timing means 29, is in turn applied to the input of the actuating means 31 via an inverter 55.

The actuating means 31 comprises a pair of D-type flip flops 57 and a switching transistor 59 which connects to a relay 61 which forms part of the relay network 25. The D-type flip flops 57 are arranged such that the output D of the timing means 29 connects to the clock input E of the first flip flop 57a and the Q output F at this flip flop in turn connects to the clock input of the second flip flop 57b. The data input 58 of the first flip flop 57a derives its input from the output 3 of the comparator 45 of the detecting means 27 , via line 56 .

Accordingly, the first flip flop 57a is clocked only by the trailing edge of the output pulse generated at the output D of the monostable 51 after it has been triggered by an active signal from the detecting means. Consequently, a high signal will only be generated at the output F of the first flip flop 57a if coincidently with the clocking of the flip flop, an active signal is still present at the output 3 of the detecting means as determined at the data input 58 of the first flip flop 57a, effectively signifying the absence of video at the common transmission line 15. Thus, if during clocking of the first flip flop 57a the output 3 of the comparator 45 returns high after initial triggering of the monostable 51, i.e. if the active signal ceases, then the Q output F of the flip flop will remain low and thus not be activated.

The data input 63 of the second flip flop 57b is permanently connected to the supply voltage Vcc and thus will cause a high signal to be generated at the Q output G of the second flip flop whenever it is clocked by a high signal being generated at the Q output F of the first flip flop 57a. The Q output G of the second flip flop 57b is in turn applied to the input of the switching transistor 59, connected in the common emitter mode. Thus, when a high signal is applied to the base input 65 of the switching transistor, the transistor will be turned on, effectively pulling the collector K thereof low and thus energising the relay 61. This in turn pulls in the contact arm of the relay which closes the sensing circuit of the VCR to which it is connected. To assist in understanding the sequence of events which occur in relation to the timing means 29 and actuating means 31, reference should be made to the timing diagram showing the voltage wave forms at the designated points of the circuit.

In summary, the relay 61 is only energised in response to detecting the absence of video signals at input 35 to the control system which are still absent after a predetermined delay period determined by the timing means

29 .

In order to ensure energisation of the relay 61 and thus appropriate control of the VCR, the Q output G of the second flip flop 57b is also connected via another switching transistor 67 to the inverting input A of the comparator 45 to provide a resetting means for the detecting means 27. The further switching transistor 67 is configured such that the output G of the second flip flop 57b connects to the base 69 of the transistor arranged in the common emitter mode, and the collector of the transistor 67 connects to the inverting input A of the comparator. This has the effect of pulling the inverting input of the comparator 45 low in response to a high signal being generated at the output of the second flip flop 57b, thereby causing the output level B of the comparator to return to a high level, i.e. ceasing the generation of the active signal. This prevents continuous triggering of the monostable 51 enabling the first flip flop 57a to return its Q output F to a low state causing the second flip flop 57b to return its Q output G to a low level and thus de-energise of the relay 61. In so deactivating the output of the second flip flop 57b, the further switching transistor 67 is turned off allowing the inverting input A of the comparator 45 to be sensitive to the output of the digital transistor 37 once more. If no video signals are still detected at input 35 of the detecting means, the inverting input A of the comparator will be returned high by the action of the digital transistor 37, prompting triggering of the monostable 51 once more and repeating the cycle of operation of the flip flops 57. Hence, the relay 61 will be repeatedly energised and de-energised, ensuring the appropriate control function is performed by the VCR.

In order to effect proper operation of the flip flops 57, it is necessary to initialise the same by setting and resetting the set pin J and the reset pin J1, respectively, thereof. This is effected by the system 23 having a further timing means 71 incorporated therein consisting of a further monostable 73 connected via an inverter 75 to the Q output G of the second flip flop 57b.

The output I of this further monostable 73 is in turn connected to the appropriate set and reset pins J of the first and second flip flops respectively so that when the output I of the further monostable 73 is triggered high, the flip flops are initialised once more after a prescribed delay. This prescribed delay is determined by the setting of the RC timing network 74 of the monostable

73. As can be seen from the diagram, the output I of the monostable 73 is triggered in response to a low signal being applied to input H thereof, which coincides with a high signal being generated at the Q output G of the second flip flop 57b.

The set and reset pins J and J1 of the flip flops 57a and 57b, respectively are also connected to the collector of another switching transistor 77 configured in the common emitter mode such that both flip flops can be initialised by applying a voltage externally to a reset input 79 connected to the base of the transistor 77.

The utility of the present embodiment can be seen when the relay 61 is connected into series with that sensing circuit which controls the stop and rewind functions of the VCR which has generating output video signals for display on the display medium. During the time that video signals are generated by the particular VCR and transmitted via the common transmission line 15 to the diaply medium, the control system 23 will be monitoring the same. As soon as the video tape stops generating video signals intended for general viewing, which usually does not coincide with the end of the video tape being screened, the control system will detect the same, and after a predetermined delay period effect closing of the circuit which controls the stop and rewind functions of the VCR. This is done by energising the relay 61 causing the contact arm thereof to close the sensing circuit enabling the appropriate control parameters to be provided to the corresponding sensor thereof and hence initiating the stop function of the VCR followed by the rewind function. This enables the VCR to relinquish control of the common transmission line 15 and return the tape to start to be ready for its next screening later in the day.

It should be appreciated that the present embodiment is described with respect to one particular type of VCR having discreet stop, start and rewind functions, and specialized control circuitry and sensors to allow automated selection of particular control functions to be performed. However, the present invention has particular application to other types of VCR, where, only two control functions are provided, namely play and stop/rewind modes. Thus, upon selecting the stop/rewind, the tracing of the VCR is stopped and rewound all in response to the selection of one specific control function. Additionally, instead of the VCR employing sensors which may be sensitive to changes in potential or current with respect to time provided by energizing passive networks which are particularly arranged to uniquely specify particular control functions to be performed, certain types of VCR now employ the selection of low ohmic connections across certain parts of the control circuitry of the VCR to allow the selection of particular control functions to be performed. Consequently, these low ohmic connections do not effect the corresponding switches of the VCR which are subject to manual operation and hence the VCR can remain operational for manual control.

It should also be appreciated that the control system need not employ the use of relays to open or close switches in the control circuit of the VCR, but rather employ semiconductor switching devices in the form of an integrated ciruict containing a number of switches or discreet components such as silicon controlled switches, switching transistors or opto couplers. Accordingly, this envisage that the present invention has equal application with VCRs employing such type of integrated circuitry in preference to relays .

Furthermore, other specific aspects of the design of the control means is not limited to hardware configurations but may alternatively be implemented in a software configuration, without departing from the spirit of the invention.

It should be appreciated that the scope of the present invention is not limited to the particular embodiment herein described. In particular it should be appreciated that the control system described in the embodiment performs one type of control function to be performed on a VCR upon detecting the absence of a video signal where previously it was present. Notwithstanding this, it should be readily apparent to persons skilled in the field of the invention that other control functions of the VCR may be effected by the control system without materially departing from the scope of the present invention.