DE2334310C3 - Circuit arrangement for determining time deviations of a composite image signal taken from a storage medium and for controlling the running speed of the storage medium - Google Patents

Description

The invention relates to a circuit arrangement as it is assumed in claim 1.

As a playback device for television recordings For example, video tape recorders are known in which a magnetic tape moves over magnetic scanning heads and video disc players where a pickup engages the groove of a rotating recording disc For such devices to work properly, the speeds of the recording medium and the Scanning device are held in a predetermined relationship to each other so that the recovered Horizontal and vertical sync pulses are stable and have a frequency that is within the synchronization range of the horizontal and vertical deflection circuits of the television receiver, with which the playback device is connected. When the information recorded is a color television signal acts in which the color information as a modulated to be processed by the playback device is recorded, the recovered signal must also be stable and have a frequency that are within the synchronization or capture range of the color circuits contained in the playback device being.

The specified relative speed between the recording medium and the scanning device can be maintained by providing a speed control of the drive motor for the recording medium in the playback device. A corresponding control device must receive information about the direction and size of any deviations from the specified relative speed between the recording medium and the scanning device. If this information is based on sensing the speed of moving parts of the playback device, then the information given to the controller is not necessarily directly related to the task of maintaining the stability and frequency of the recovered television signal within a desired synchronization range of the signal processing circuitry. For example, in the case mentioned, an incorrect operation of the playback device, which can be attributed to a slip between the recording medium and the drive mechanism, is neither detected nor corrected

It is known from US-PS 29 13 652, a time signal together with the information to be reproduced on the recording medium. At a In such a system, the recovered time signal is used to provide information about the playback to obtain the relative speed between the recording medium and the scanning device. However In this case, too, the information supplied to the control device is not directly related on the task, the stability and the frequency of the recovered television signal within one to keep the desired synchronization range of the signal processing circuits. If that is what was recorded Time signal is not exactly related to the recorded information or if there is a problem when playing back a distortion occurs in the time signals and the information signals (for example, due to bending or a stretching of the record carrier), then the time error in the recovered TV signal neither felt nor corrected While in the case of US-PS 29 13 652 a dated Storage medium picked up impulse with its delayed by the distance between two corresponding impulses Version is compared and a correction signal for the running speed from the comparison result of the storage medium is generated in the sense of keeping a desired pulse interval constant in contrast, according to DTPS 11 06 799 and OE-PS 2 86 384, the comparison of a regular recurring signal component with a reference frequency that must be as constant as possible so that the Running frequency of the storage medium is kept constant to the desired extent. According to the GB-PS 8 24 041, a signal component is also compared with its delayed version, but the delay in this case determined by the running time of a magnetic tape between two magnetic heads DT-AS 12 61543 also uses a reference frequency and causes the correction of detected time errors

ler by engaging maturity güedern with gestaf felter delay time, with the activation of the required delay elements with the help of off 4comparison derived control signals takes place

The object of the invention is to achieve the achievable To improve the accuracy of the regulation in relation to the effort and a special one in this regard indicate appropriate arrangement. This task is achieved by the characterizing features of the claim 1 solved

- While the known circuits, as far as they are comparable with the invention, with Analog signals work and use of an analog control of the running speed of the storage medium make, the regulation according to the invention takes place in a digital manner, which is known with respect to the achievable accuracy in relation to the effort is more advantageous The corresponding binary Circuit elements and their interconnection are now the subject of the new protection request.

According to the invention, the arrangement is such that the braking device for the storage medium drive is only switched on when a delayed input signal is fed to a bistable multivibrator will. If the turntable runs too fast, it hits delayed input impulse first arrives at the multivibrator, which then comes into a switching state in which the braking device is not activated. A short time later, the delayed pulse appears on the other Input of the multivibrator and switches it to a state in which the braking device is operated. This state remains during the current line interval, so that the turntable until the next line pulse occurs. Is its speed then still too high, then the same thing repeats itself. If, on the other hand, the speed has already dropped below the target speed, then the delayed pulse appears first on the multivibrator, which thus still remains in the braking position, but switched back to the other position when the instantaneous pulse occurs shortly thereafter where it generates a brake release signal, the turntable So it is not braked any further, but rather it is driven back to a higher speed can be brought. In a practical case, a rotation speed of the turntable rm could be about 450 RPM and a line pulse spacing of 63.5 μβ die Carry out control very sensitively.

To explain the invention, exemplary embodiments are described in detail below with reference to drawings described.

F i g. 1 shows, partly in block form, the circuit diagram of an arrangement according to the invention for detection of timing errors and speed regulation;

F i g. 2 is another embodiment of an arrangement according to the invention for detecting timing errors and speed control, which is particularly suitable for playing back color television recordings is

In the case of the in FIG. 1 is the arrangement shown a video disk 12 as a recording medium on the turntable 14 of a video disk player. The turntable 14 is made of conductive material and is connected via a transmission belt 15 and a pulley 17 driven by a motor 16. The motor is a synchronous motor with a synchronous speed of 3600 Revolutions per minute. The diameter of the turntable 14 and the diameter of the pulley 17 are chosen so that the turntable in the free running state has a speed (455 rpm) that is slightly is greater than its speed in normal operation (449, 55 rpm). It should be noted that the number of lamellae

so chosen in the rotor and in the stator of the Syachron motor is that desired; Engine torque is obtained. A braking system 18 slows the speed of rotation of the turntable 14 in order to prevent the turntable from being driven too quickly by the motor

ic 16 equalize.

The video disk 12 is touched by a scanner 20 With relative movement between the plate 12 and the scanner 20, the recorded on the plate Television information is acquired at terminal 22 of the The signal-processing circuit arrangement 24 of the playback device is supplied. The circuit arrangement 24 wins from the signals fed to terminal 22, a television signal mixture which is sent to the output terminal 26 appears and contains sync pulses

The composite signal appearing at terminal 26 is transmitted via terminal 28 of the playback equipment a television receiver 30 supplied. If necessary, this can be done at the terminal 2t; appearing composite signals a carrier wave and in this form the antenna connections (not shown) of the television receiver 30 are supplied.

The composite signal appearing at the terminal 26 also reaches the connection 34 via a line 32 a separator 36 for synchronizing pulse separation.

The separator 36 and other related circuits provide a useful signal, which is with the horizontal deflection frequency (line frequency) of the recovered composite video signal. This useful signal is sent to a delay line.

led, which delays it for a period of time, which corresponds to a normal line length in the video signal By comparing the delayed with the undelayed A useful signal, an error signal is generated, which is fed to the brake mechanism 18.

The brake mechanism 18 reduces the speed of the turntable 14 and sets the relative speed between the video disk 12 and the scanner 20 so that the timing errors in the recovered video signal disappear.

The terminal 34 is via a resistor 35 and a capacitor 37 to a differential amplifier 38 connected. The differential amplifier 38 can be an integrated circuit, as described under the type designation CA 3028 A purchased from RCA Corporation

is offered. A description of this integrated circuit can be found in an RCA publication entitled "Finear Integrated Circuits, File No. 400 «, which is provided by RCA Electronic Components, Harrison, New Jersey, USA. The dif-

differential amplifier 38 is biased so that it is im non-linear range works. It receives its operating voltages via resistors 40,42,44,46 and 48 from a terminal 50, which is supplied with 1-15 volts DC voltage. The terminal ÜO is equipped with a discharge

capacitor 56 connected for signal frequencies. External load resistors 52 and 54 for the differential amplifier are located between terminal 50 and the integrated circuit.
The output of the differential amplifier 38

is fed to an emitter follower 58. The waveforms of the voltages on terminal 34 (i.e., at the input of the separator 36) and on the emitter of the emitter follower 58 are shown in FIG. 1 shown. The connection to port 34

The composite video signal is amplified in a non-linear manner, with the negative components of the signal (the sync pulses) being amplified more than less, negative or positive components. The JEinitterfolgerÄ is a resistors 62 .üi} ^ '{M;und''i ^ 6: ligand Sato, rieii.6jS and 68 containing Jießp ^ ßfilter.lW yerbunden 70 to the base of Separatortransi- ^ _tprs: ICQ. The transistor 70 is biased to the threshold of its conductivity by resistors 72 and 74. The negatively directed sync pulses drive the transistor far into the conductive area, so that a voltage is created across resistor 76

The voltage curve at the collector of transistor 70 is shown in the drawing next to this component The sync pulses pass through a blocking diode 78 to an integrator circuit with the Resistors 80 and 82 and capacitor 84. The integrator circuit prevents equalization or Surge voltages with a duration of less than about 5 microseconds (the duration of a horizontal sync pulse) bias transistor 86 forward. When the voltage across resistor 82 and at capacitor 84 reaches a value which switches transistor 86 on, then the voltage on falls Connection point of resistors 88 and 90 to the value of the ground potential, creating a monostable Multivibrator 92 is triggered.

The monostable multivibrator 92 provides a negative going output pulse of 45 microseconds Length of time. If the input terminal 34 of the separator during the vertical blanking interval equalization pulses are supplied, then these pulses cannot interfere with the operation of the system. The compensation pulses appear at connection 34 approximately every 31.5 microseconds, during the vertical blanking interval. The first compensation pulse triggers the monostable multivibrator 92 off, and the next compensation pulse appears after the multivibrator has been triggered during of the 45 microsecond output pulse. The second compensation pulse therefore has no influence on the multivibrator and does not trigger any further output impulses.

The output signal of the monostable multivibrator 92 reaches a further monostable multivibrator 94, which, if triggered, produces a negative output pulse of 5 microseconds in duration This creates a series of impulses, the duration and timing of which correspond to the horizontal sync impulses in the input signal fed to terminal 34. The multivibrators 92 and 94 increase the reliability of the system by preventing the rest of the system from entering unwanted signals are fed in.

The output pulses of the separator 36 are applied to the base of a normally conductive transistor 100 via a line 98 and a capacitor 99. This transistor receives its operating voltage via resistors 101 and 103 from the supply terminal 50 which is at +15 volts DC voltage. The pulses coming from the separator 36 periodically put the transistor 100 into the blocking state. The positive voltage pulses then appearing at the collector of the transistor 100 reach the base of a transistor 102 via a capacitor 105. A resistor 107 normally keeps the transistor 102 in the conductive state. The pulse appearing at the connection point between the capacitor 105 and the resistor 107 blocks the normally conductive transistor 102, whereby the current flow from the terminal 50 via a resistor 109, the emitter-collector path of the transistor 102 and a resonant circuit tuned to 3.58 MHz Ul is interrupted.

The resonant circuit 111 contains a tunable coil 104 and a capacitor 106. A resistor 110, which is bridged for signal frequencies by a capacitor 108, represents the collector load for the transistor 102 in its conductive state. When the transistor 102 is blocked, the resonant circuit is 111 made to vibrate at a frequency of 3.58 MHz. When the transistor 102 becomes conductive again after the positive voltage at its base has dropped, the oscillation breaks off. The 3.58 MHz oscillating pulse generated is applied to the base electrode of a transistor stage 112 connected as an emitter follower. The output signal of the emitter follower 112 arrives at a monostable multivibrator 118 via a resistor 114 and a capacitor 116 . The output of the emitter follower 112 is additionally connected via a resistor 120 to the input terminal 122 of a delay line 124 , the delay time of which is 63.5 microseconds. Such a delay line is often referred to as "1 Η delay line" because their delay time corresponds to the duration of a horizontal scan of the information of the video signal, the delay line 124 is an acoustic delay element with glass material whose pass band is centered at 3.58 MHz The input impedance of the delay line 124 is tuned to 3.58 MHz by means of an adjustable coil 126. The output impedance of delay line 124 is similarly tuned to 3.58 MHz by means of an adjustable coil 130 connected to output terminal 128 of the delay line Resonant circuit 111 is tuned to the center frequency of the delay line 124 should be the center frequency of the delay line

124 are changed, then the resonance frequency of the oscillating circuit 111 must be changed accordingly. Each 338 MHz oscillation pulse applied to the input terminal 122 of the delay line appears at the output terminal 128 of the delay line after a delay of 633 microseconds. The delayed oscillation pulses pass through a resistor 132 and a capacitor 134 to an amplifier stage 136, which has an amplifier 138 in the base circuit and an amplifier 140 in the collector circuit

SS tion (emitter follower) contains the delayed and amplified swing pulses are then passed through a capacitor 142 to a monostable W multivibrator.

The output signal of the monostable multivibrator 118, which is triggered by the leading edge of each undelayed 338 MHz oscillation pulse, and the output signal of the multivibrator 144, which is triggered by the leading edge of each delayed 338 MHz oscillation pulse, are both fed to a comparator 6s stage 146 Comparator stage 146 can be a bistable multivibrator which can assume one or the other of two stable states, depending on which of its input terminals 148 and 15

is applied. When terminal 148 is energized, comparator 146 provides +4 volts DC at its output terminal 152, and when terminal 150 is energized, output 152 has ground potential. Simultaneous application of input terminals 148 and 150 has the consequence that the voltage at the output of the comparator does not change its previous value. The output signal of the comparator 146 is characteristic of the order in which the monostable multivibrators 118 and 144 are triggered. This in turn is directly related to the frequency of the horizontal sync pulses in the video signal which is fed to the input terminal 34 of the separator 36.

As the relative speed between the video disk 12 and the scanner 20 increases, the instantaneous 3.58 MHz oscillating pulse actuates the monostable multivibrator 118 before the delayed 3.58 MHz oscillating pulse actuates the multivibrator 144. The delayed oscillation pulse owes its origin to the immediately preceding oscillation pulse which already occurred at a point in time before the increase in the relative speed.In this case, the monostable multivibrator 118 sends an output signal to the comparator input 148 a little earlier than the monostable multivibrator 144 an output signal to the comparator input 150 supplies. The corresponding signal states at the inputs 148 and 150 of the comparator have the consequence that the potential at the comparator output 152 first rises to +4 volts and then drops to ground potential. The ground potential remains for about 63.5 microseconds. After this time, a new 3.58 MHz oscillation pulse actuates the two monostable multivibrators 118 and 144, which in turn feed signals to the comparator.

If the relative speed between the video disk 12 and the scanner 20 remains high or continues to increase, the multivibrator 118 receives a 3.58 MHz oscillation pulse before the delayed version of the 3.58 MHz oscillation pulse ( previously supplied to the multivibrator 118 ) reaches the multivibrator 144 and the process described above is repeated. If the relative speed between video disk 12 and scanner 20 has decreased so much that the two monostable multivibrators 118 and 144 receive 338 MHz oscillation pulses at the same time, then the ground potential at comparator output 152 remains unchanged for about a further 634 microseconds.

If the relative speed between the video disk 12 and the scanner falls below its target value, the monostable multivibrator 144 receives a delayed oscillation pulse before an oscillation pulse reaches the inonostable multivibrator 118 Relative speed occurred in, while the delayed oscillation pulse owes its origin to the vibration pulse generated immediately before, which occurred before the decrease in speed.In this case, the comparator at its input 150 receives a signal from the multivibrator 144 a little earlier than a signal from the multivibrator 118 at Comparator input 148 is received. This Signalkom- H bination to the comparator inputs 148 and 150, with the result that the potential at the first comparator output 152 drops to ground potential and then descends to +4 volts. The positive potential is maintained for about 63.5 microseconds, and at the end of this period of time 3.58 MHz oscillation pulses are again applied to the two monostable multivibrators 118 and 144, whereby signals are again fed to the comparator 146.

If the relative speed between video disk 12 and scanner 20 remains low or falls even further, an oscillation pulse (previously supplied to multivibrator 118) is given to multivibrator 144 before multivibrator 118 receives an oscillation pulse, and the sequence described above is repeated. If the relative speed between video disk 12 and scanner 20 has increased so much that the two multivibrators 118 and 144 receive oscillation pulses at the same time, then the positive potential at comparator output 152 remains unchanged for approximately a further 63.5 microseconds. If the relative speed between video disk 12 and scanner 20 increases above the setpoint value, then the arrangement operates in the manner described above.

The comparator 146 supplies a binary output signal which is characteristic of the frequency of the horizontal sync pulses of the video signal is the one taken from the recording medium and in the signal processing Circuit arrangement 24 is processed. When the frequency of these sync pulses is too high for some reason, the comparator 146 provides signals at its output 142, the one Cause a reduction in the relative speed. With a decrease in the relative speed the frequency of the horizontal sync pulses is lower. On the other hand, if the frequency of the horizontal sync pulses is low for some reason then comparator 146 provides at its output 152 signals that lead to an increase in the relative speed. With a higher relative speed the frequency of the horizontal sync pulses also increases. The comparator 146 can also be different Be a device as a monostable multivibrator and provide an analog output signal at output terminal 152, which is based on the time relationship of the signals fed to the comparator inputs 146 and 150 In this case a suitable arrangement would have to be connected downstream of the comparator, which the Uses analog signal for speed control of the drive

The comparator output 152 is through a diode 146 to the base of a normally conducting transistor 156 connected. The transistor 156 is by means of the DC voltage present at the terminal 50 above the Resistors 158 and 160 forward biased when comparator output 152 is ground potential then the transistor 156 is blocked; and when the comparator output 152 is at +4 volts then transistor 156 remains conductive. The collector of transistor 156 is connected directly to the base of a normally non-conductive transistor 164. The KoHektor-emitter path of the transistor 164 is in series with an iron core coil 166 between a terminal 168 and ground. Terminal 168 is connected to +40 volts DC and for AC signals connected to ground through a capacitor 170.

The iron core coil 166 is located in the vicinity of the metal turntable IH so that the Turntable represents part of the path of the line of force for the magnetic field of the iron core coil when electricity

609 684 287

flows through the coil 166, a magnetic field is created which induces eddy currents in the metal of the turntable 14. These eddy currents generate a magnetic field, which interacts with the magnetic field of the iron core coil 166, creating a braking force that counteracts the rotation of the turntable 14 caused by the eddy currents The force is sufficiently strong to slow down the rotation of the turntable and to set the correct relative speed between the disk 12 and the scanner 20 so that the horizontal sync pulses in the recovered video signal have the desired frequency.

The braking force caused by eddy currents has the consequence that the turntable 14 with a rotary ij number rotates that is asynchronous with respect to the speed of the pulley of 3600 rpm The asynchronous Operation is brought about by the drive belt 15. The drive belt 15 is made of elastic material such as neoprene rubber or polyurethane and has s a rectangular cross-section of

SM2 mm χ 0.508 mm The belt forms a media nism for the controllable, reproducible linear speed change, whereby the creep strain of the belt is used.The drive belt 15 is pulled around the circumference of the pulley 17 and the turntable 14 and thereby around 10% of its non-abutting inner circumference Stretched by 73.66 cm. The stretching is adjusted by a suitable choice of the distance (15.72 cm) between the axes of rotation of the pulley 17 (diameter 91 cm) and the turntable 14 (diameter 24.22 cm).

It was found that the braking effect caused by the eddy currents the speed of the plate - ^; Lers can reduce from 455 rpm (in the free-running state) to 445 L "min without a slip occurring between the drive belt 15 and both the pulley 17 afc and the turntable t4 More precisely, the braking leads to a stretching of the belt section running from the turntable and to a compression of the part of the belt running towards the turntable, without a slip occurring between the drive belt on the one hand and the pulley 17 and the turntable 14 on the other hand.

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- "described coupling around Braking caused the engine load and flow hence the slip speed of the motor to regulate the speed of the turntable. The effect the slip speed in the motor 16 can with the above-described creep effect of the belt drive be combined.

If the comparator output 152 drops to ground when the player is operating, then the transistor 156 is blocked, whereby the transistor 164 becomes conductive This corresponds to a state, where the frequency of the horizontal sync pulses of the recovered video signal is above the target value located. When the transistor 164 is conductive, current flows through the iron core coil 166. This results in a braking force Slowing down the rotational speed of the turntable 14 is exerted. The rotational speed of the turntable 14 becomes so much decreased until the frequency of the horizontal sync pulses of the recovered video signal ur. The setpoint drops. At this point in time, the> potential at the comparator output 152 becomes positive, and the Transistor 156 becomes conductive This blocks transistor 164, and the flow of current through the Iron core coil 166 stops. so that the braking force disappears. As the braking force disappears, the Speed of the turntable 14 to the idle speed (i.e., the speed with the turntable idling). When a point is reached where the frequency of the horizontal sync pulses of the recovered video signal is too high, the process of repeats itself itself. It can be seen that the speed of the turntable is constantly readjusted in order to obtain the correct frequency of the horizontal synchronization pulses of the recovered video signal for normal operation. Devices for color coding in playback devices for television recordings have been proposed in which the recovered video signal is decoded by circuits including a delay line. Such a color coding system. is in the USA. Patent 35 SQ 635 discloses, however, for these systems to work properly the time interval between each horizontal scan line of the recovered video signal is exactly that Be adapted to the delay time of the delay line used in the Deoodiersohaltungen. When the relative speed between the recording medium and the scanning device is such that the If the interval between the lines of the recovered video signal is not adapted to the delay time of the delay device, then the decoder circuits will not work correctly.

in Fig. 2 is a system 200 rar reproduction a « Mtgeaektaeten Farbnsehagnab. shown The m Systems shown in the dashed frame 3ΘΘ is similar to the system according to the USA patent specification * 3560635. An engine 202 powers an AafeeJcb Very tightly, ta «« wipe this and a scan “I saw a relative movement in 201 The color television signal is reflective

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the switched "1 H delay lines" 208 and 210 each with a delay time of 63.5 microseconds. The entire composite video signal arrives at a delay network 212, where it delays in order to produce an adaptation to the delay in the low-frequency color information caused by the low-pass filter 206.

The output signals of the low-pass filter 206 and the delay network 212 are applied to a subtraction circuit 214 , where the low-frequency color signal is subtracted from the delayed composite video signal. The high-frequency luminance signal therefore appears at the output of the subtraction circuit. This high-frequency luminance signal and the delayed low-frequency color signal from the delay line 208 are added in an adder 216 . In a similar manner, the high-frequency luminance signal and the twice-delayed low-frequency color signal coming from the delay line 210 are added to one another in an adder 218. The output signals of the adders 216 and 218 and the output signal of the delay network 212 are fed in parallel to each of the three individual decommutating switches 220, 222 and 224 .

A decommutating clock circuit 228 receives the recovered color television signal and senses synchronization signals recorded on the recording medium. These synchronizing signals mark the beginning of each three-line sequence of the color information. The clock circuit 228 controls a synchronizing device 226 which is coupled to the three switches 220, 222 and 224. These switches are controlled by the synchronizing device 226 in such a way that they operate in synchronism with one another and in synchronism with the line-sequential color signals. The switches are operated periodically in such a way that a signal constantly appears at the output terminal of each switch which contains only one of the three color information and the luminance information. Thus, a low-frequency signal containing the color information for red and a high-frequency signal containing the luminance information appear at the output 230 of the switch 220. A low-frequency green signal and a high-frequency luminance signal appear at the output 232 of the switch 222 , and a low-frequency blue signal and a high-frequency luminance signal appear at the output 234 of the switch 224. It has been found that the delay lines contained in the reproduction system 200 , as well as the signals which have passed through the delay lines, can thus advantageously be used for the speed control device 235 of the reproduction system. The horizontal sync pulses of the recovered video signal appear at a repetition rate of 15,734 kHz. This frequency is in the pass band (0 to 600 kHz) of the low-pass filter 206. Therefore, the horizontal sync pulses passing through the delay line 208 or 210 can be used in a similar speed control device as shown in FIG. 1 was described. It should be noted that any other signal which occurs at a line frequency and runs through one of the delay lines can also be used as a useful signal for the control device 235.

In the embodiment according to FIG. 2, the horizontal sync pulses of the recovered video signal pass through both delay lines 208 and 210. The input and output of delay line 208 are connected to separator stages 236 and 238 for separating the horizontal sync pulses. The separated horizontal sync pulses from the output of the separator 236 are sent to a comparator 240 via a pulse shaper 239 . The delayed, separated horizontal sync pulses from the output of the separator 238 are applied to the comparator 240 in a similar manner via a pulse shaper 242 .

The comparator 240 provides an output signal which is characteristic of the frequency of the horizontal sync pulses of the recovered video signal. The comparator 240 is connected to an error signal generator 244 which controls the drive mechanism 202. The drive mechanism, under the control of the output signal of the error signal generator, adjusts the relative speed between the recording medium and the scanner so that frequency changes of the horizontal synchronizing pulses of the recovered video signal are corrected. The comparator 240, the error signal generator 244 and the drive mechanism 202 operate similarly to the corresponding egg rieh long in Fig. 1 to achieve the same result as there.

It should be noted that many "1H delay lines" operate extremely accurately and within tolerances that are closer than the stability and synchronization range of the deflection and color circuits of many television receivers. However, since the device for detecting line errors and for speed control is as precise as the delay time of the delay lines contained in the playback device, the recovered video signal is kept exactly at the exact frequency required when the signal processing circuits of the playback system are less precise delay lines services included. Thus, the present system allows cheaper delay lines to be used in the signal processing circuits without sacrificing reproduction quality

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: '■ 1. Circuit arrangement for determining time deviations of a composite image signal taken from a storage medium by means of a scanner and for controlling the running speed of the storage medium with respect to the scanner with the aid of an error signal, which is determined by comparing a signal component that recurs regularly at the line frequency and is delayed by one line duration with the corresponding undelayed signal component is obtained, characterized by a first pulse generator (118) which generates a first trigger pulse when the undelayed signal component is supplied, a second pulse generator (144) which generates a second trigger pulse when the delayed signal component is supplied, and a bistable multivibrator (146 ), the inputs of which are each connected to one of the pulse generators (118, 144) and the first trigger pulse only at the first input produces an output signal (brake release signal) and when the second trigger is only at the second input gerimpuls supplies another output signal (brake signal) which is fed to a brake device (164) known per se for the storage medium drive (14). 2. Circuit arrangement according to claim 1, characterized in that the control signals for the pulse generators (118,144) are derived from the line synchrcnimpuls separated from the image signal mixture by the latter being fed to an oscillation train generator (100, 102, Ui), which generates oscillations occurring periodically at the line frequency , the oscillation frequency of which is in the pass band of the delay element designed as an acoustic delay line (124) with bandpass property, which causes the delay by one line duration, and which are supplied to the first pulse generator (118) without delay, but to the second pulse generator (144) after passing through the delay line (124) .