DE1220469B - Magnetic tape recorder for recording and / or playing back broadband signals, in particular television signals - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

H04n

German class: 21 al - 33/11

Number:
File number:
Registration date:
Display day:

A 31545 VIII a / 21 al

March 9, 1959

7. Ml 1966

The invention relates to a magnetic tape recorder for recording and / or reproducing Signals in a wide frequency range, which can also include television signals, for example.

In already known magnetic tape recorders of this type, the recording takes place in the form of successive track parts running transversely or diagonally across the magnetic tape, which are magnetically recorded on the sand by a rotary head arrangement with several head units or are chamfered by it. The magnetic tape is held in a curved shape in front of the rotary head arrangement by a concave guide device, so that it is located over its entire width in close proximity to the arc-shaped working path of the head units that sweep the tape one after the other.

Ehje widespread practical application of such systems is recording or playback of television programs.

The position of the concave tape guide device determines the depth to which the circumferential Head units press in the magnetic tape they have coated. There is a certain pressure of contact necessary; however, excessive pressure leads to unnecessary wear and tear on both the magnetic tape as well as the head unit. Due to the contact pressure between the head units and the magnetic tape this is stretched somewhat in the longitudinal direction of the track during the sweep by the heads. This can lead to clock skew or phase errors. The amount of stretch affects the time it takes a head unit to cover two points of the information track on the tape. A difference between the head when recording on the one hand and playback on the other-: on the other hand, the times required for the crossing of two such points leads to timing errors in the reproduced Signal. Further influences that can cause differences in scanning or scanning times between recording and playback and thus of timing errors the wear of the head units, the effective radius of which thereby becomes smaller, the contraction and expansion of various pieces of equipment as a result of temperature fluctuations and the expansion or shrinkage of the magnetic tape due to temperature and humidity fluctuations.

The main purpose of the invention is to provide in a magnetic tape recorder of the type in question for an automatic correction of phase errors caused by changes in the pressure between the magnetic tape and the head units in the magnetic tape recorder for recording and / or
Playback of broadband signals,
especially television signals

Applicant:

Ampex Corporation, Redwood City, Calif.

(V, St. A.)

Representative:

Dipl.-Ing. F, Werdermann, patent attorney,

Hamburg 13, Innocentiastr. 30th

Named as inventor:

Robert Fred Post, Mountain View, Calif .;

William Barnhart, Palo Alto, Calif. (V. St. A,)

Claimed priority:

V. St. v. America March 10, 1958 (720 329)

Playback versus recording.

In an already known device for reproducing television or other Signals recorded on a moving magnetic carrier and message components as well as a substantially constant frequency auxiliary signal, for example synchronizing pulses, is made up of the auxiliary signal taken from the moving carrier and a frequency constant Comparison signal obtained by phase comparison, a control signal that controls a controllable delay stage in such a way that it is also from the moving Carrier removed television signal or other signal through the delay stage in the sense of a Reducing the phase difference is more or less delayed to phase differences in the signals compensate by delaying the reproduced signal.

It is also the subject of an older proposal to compensate for the effects of shrinkage or expansion in the case of magnetic recording media due to dimensional inaccuracies of the apparatus and the contact pressure to compensate for the wear and tear of the magnetic scanning heads to make adjustable between the magnetic tape and the head units.

The proposal for solving the problem on which the present invention is based is to

609 588/273

3 4

that the tape guide device for controlling FIG. 14 is a circuit diagram, partly as a block contact print - between the magnetic tape and the diagram showing the grounding of the sensing unit Head units in the direction of their distance to the purifies, which the error signal from the reproduced Rotary head arrangement arranged movably and forms by signal, and

Devices Dependent on One in Fig. 15 is a detailed circuit diagram

Reproduction of any phase errors in the signal from a suitable sensing unit.

derived error signal is controllable in such a way that As FIGS. 1 and 2 show, the magnetic

the phase errors in each case by changing the calming band 11 in the longitudinal direction on the head arrangement 12

Approximate pressure between the magnetic tape and the moved by means of a drive roller 13, which in

Head units are corrected. io connection with a freely rotating counter pressure

According to a further proposal of the invention, roller 14 works. On the circumference of a head drum It can be advantageous to have a tape guide unit 18 driven by a synchronous motor 19 Direction is used, which is the current magnetic, several magnetic head units 16 are attached through depending on the error signal. A guide device 21 is used to control the arching Holds negative pressure (suction air). To form 15 ben the tape while it is attached to the head units of the error signal can be pulled past as a function of. If the head units have a sweep between predetermined horizontal sync pulses circular arc-shaped path is located The device operating in the event of cycle errors keeps the belt in constant pressure contact with the magnet will. ■ »· ■;: ..". The tape 11 is taken from a supply reel

The ao 22, which receives the horizontal sync pulses, is fed to a take-up reel 23 Facility can be used to form a around a reference. wrapped. The tape is at the magnetic head assembly level Fluctuating output signal serve, from the voltage 12 by suitable, it self-adapting from a ^ testing device for the purpose of forming guide pins 24 and 26 and rollers 27,28 of bypassing the phase errors between the predetermined ones. The supply reel and the take-up horizontal sync pulses Proportional error coil can, as usual, be carried on winding disks and a sample can be taken at a time. . will. In a known manner, motors for the

The “periodic removal of a sample ” winding plates can be provided.

The test device used can be used depending on In operation, there is one head in each case to switch over ^: the head units when being fed with the tape. The heads are controlled by combining the overall signal 30 to be reproduced in a commutator 29 with the switching pulses required for electronic parts. . of the system as shown in FIG. 1 and 2 scheme

The invention is explained below with reference to the drawing. The commutator can e.g. B. grinding, for example, explained in more detail. In this case, rings that are each connected to a head and, for the sake of clarity, will have the entire stationary brushes that are in grinding contact with the associated system of a magnetic tape device of the rings initially set,
mentioned genus, which of the present When recording a signal, the inventions are further developed accordingly: speeds of the head drum 18 and the drive

1 is a block diagram showing a magnetic roller 13 held in a specific relationship. At the

represents handset according to the invention; Playback process is this relation within

Fig. 2 is a plan view of a suitable narrow boundary in the same manner as the on-tape transport arrangement; drawing adhered to. To this end, through

Fig. 3 is a block diagram showing a system a magnetic head 31 a control signal on a

to regulate the pressure between the tape and the head control track along one side wall of the tape

explained; .. recorded. The control signal is used when the

Fig. 4 is a plan view of a magnetic 45 would be scanned, amplified and used to control the treadmill according to the. Invention; speed relation of drum and drive

Fig. 5 is a side view of the device after roll used. A recording head 32 serves

Fig. 4; . to record the sound information on the other

F i g. 6 is a sectional view taken along line 6-6 of the side edge of the magnetic tape. Erase heads 33

of Fig. 5; 50 and 34 for the audio track and the control track

F i g. 7 is a sectional view taken along line 7-7 leading heads 31 and 32, respectively,

of Fig. 5; - - * The one shown in the block diagram of FIG

F i g. 8 is a cross-sectional view taken along line 8-8 of the electronic circuit in the speed

from F i g. 4; The control part and the electronic signal part

Fig. 9 is a. End view in enlarged 55 parts. For a better understanding of the invention are

the stab in FIG. 4 and 5 shown tape guide the two circuit parts are described separately.

Adjustment device; A control frequency source 36 supplies the control

F i g. 10 is a side view of the tape guide frequency for the device in recording and recording

Adjustment device of FIG. 4 and 5; during playback. The frequency 36 can e.g. B.

11 is a block diagram of a switching device 60, the 60 Hz line frequency, or it may consist of one

device for performing the switching operations in the crystal-controlled oscillator can be taken. the

Device according to Fig. 1; Frequency of the power source 36 may, for example

F i g. Figure 12 is a block diagram that suggests a suitable 60 Hz. It is transferred to a frequency multiplier

Fade switch for use in conjunction with fan 37 placed at a higher frequency signal

the one shown in FIG. Figure 1 shows the system shown; 65 to put on the amplifier 38. In the following

Fig. 13 shows the waveforms at various discussion assuming that the multiplier

Parts of the shown in FIGS. 14 and 15 carry out a multiplication by four times, so

Circuits which form the error signal; that the frequency applied to the amplifier 38

240 Hz signal is. The amplifier 38 is preferred a three-phase booster that is suitable for driving the three-phase synchronous motor 19. As already mentioned, the motor 19 drives the head drum which carries the magnetic heads 16.

A circumferential disk 39, half black and half white, is carried by the motor shaft. A light source 41 is focused on the disk, and the light reflected from it is through a photocell 42 added. The output from photocell 42 is approximately a square wave of a frequency which is equal to the speed of the motor 19. For the example given, the Square wave signals have a frequency of 240 Hz.

The output from the photocell 42 is passed through a pulse shaper 43 and to a frequency divider 44, which is used to subdivide the frequency. In the embodiment, the divides Divide 44 by 4 to produce a 60 Hz frequency for filter 46 in this way. The latter is preferably a band filter which forms an approximately sinusoidal output signal. During the recording process the output of the filter 46 is applied to an amplifier 47, and the amplified The signal is used to power the drive motor 48 of the capstan. The belt drive motor is therefore driven at a speed which is directly dependent on the speed of the head drum 18 is. In practice, the tape drive roller is to a certain extent inevitable by the head drum "guided". The tape moves a predetermined amount during each complete revolution of the head drum Longitudinal stretch.

The output from the pulse shaper 43 is applied to a control signal amplifier 51 via a filter 49, its output during a recording process to the recording head 31 for the control signal is fed.

During playback, the control signal 36 is again applied to the frequency multiplier 37 and amplified and supplied to the synchronous motor 19. This drives the head drum at approximately the correct speed for scanning the prerecorded transverse recording track. The photocell 42 in turn depicts a signal that is shaped and passed through the filter 49. The signal from the filter 49 is applied to a phase comparator in the drive roller servo amplifier 52. A The second signal is applied to the phase comparator from the control signal amplifier 53, which is connected in such a way that that it receives the output signal from the control signal head during playback. The phase comparator produces a resultant signal of a frequency that is a function of the phase difference between the signals and the photocell. The signal is passed through a filter to the grid of a reactance tube placed, which is one of the frequency-determining elements of a common Wien bridge oscillator is. The oscillator normally operates at the recording frequency (in the exemplary embodiment 60 Hz), but the frequency is increased and decreased by the signal from the phase comparator modified. The output is fed to amplifier 47 which drives the capstan motor drives and controls its speed. The drive roller motor therefore guides the belt during each rotation the head drum by a predetermined distance, so that the heads 16 the recording track scan precisely on the magnetic tape.

The effect of the system described is that the drive roller is made to with playback in exactly the same relation within close confines of the drum 18 of the rotary head assembly walking around as it did during the recording process. Is the drum once to the middle of a track at the beginning of playback

ίο set, the system automatically maintains the relationship constant, and the rotating magnetic head units constantly scan the recorded transverse tracks exactly from.

As already stated, the lower part of FIG. 1 contains the signal part of the electronic circuit. The only connection between the signal part and the control part of the electronics is the connection between the output filter 49 and the switching device 61. The signal from the filter 49 becomes used to control the switching from one playback head to the next during playback to to form a composite signal corresponding to the recorded signal.

The recording electronics can consist of a device serving to generate a modulated carrier in conjunction with suitable recording amplifiers. FM recording (frequency modulation recording) is preferably used, but AM (amplitude modulation) can also be used. Assuming the use of FM recording, the recording electronics may include a modulator 62 which receives the input signal and a recording amplifier 63 which is connected to receive the output signal from the modulator. The output signal from the recording amplifier 63 is applied continuously to the individual head amplifiers 66 to 69. When recording, the switch 71 is set so that it connects the magnetic heads 1 to 4 with the amplifiers 66 to 69.

As already mentioned, FM recording is preferred. Some kind of FM recording, which are used for satisfactory recording and reproduction of television images is described in British Patent 798,927.

During playback, the switch 71 is placed in such a position that the output of each Head individually to the preamplifiers 72 to 75 belonging to it. Your output signal is fed to a switch 61. A single channel frequency signal (combined Signal) is supplied to the demodulator 76. The switch is used to activate the individual outputs of the amplifier 72 to 75 one after the other and alternately toggle electronically if the corresponding heads stroke the tape. The output of the switch is a signal corresponding to the recorded signal composite signal.

When recording, it is necessary to derive the amplified output signal from one head at a time, switching from one preamplifier to the next in an instant while the signal is in progress where the least possible distortion is carried over into the reproduced signal. It For example, an electronic switching device can be used as shown schematically in FIG. 11 is; it contains four interrupters 81 to 84, which as

Individual switches work for the signals from each of the four preamplifiers. The control impulses for these tubes are derived from the original square wave generated by the photocell. The rights wave is amplified and filtered and enters the switching device as a 240 Hz sine wave. task it is this to develop the progressive impulses from this original time or clock signal, which are necessary to switch the tubes 81 to 84 at the correct time in each case.

The 240 Hz signal from the photocell passes through the variable phase shifter circuit 86 and is amplified by an amplifier 87. By applying the signal to a full-wave rectifier, the output base frequency of which is 480Hz, the frequency is doubled. The harmonics are removed by a bandpass filter to create a clean 480 Hz signal for stage 89, which acts as an amplifier and limiter. With 88 the combination of the full wave rectifier and the filter mentioned is referred to. The amplifier and limiter stage 89 converts the input into a square wave with set edges or into a pulse. This pulse is then applied to the phase splitter 91 , the two output signals of which are phase-shifted by 180 °. The pulse lying in one phase is fed to the protective grids of the switching tubes 81 and 82 and the phase-shifted components are fed to the protective grids of the tubes 83 and 84.

The 240 Hz signal from the amplifier 87 is also fed to the two identical amplifier and limiter stages 93 and 94. After entering one of these channels, one of the signals is shifted by 90 ° with respect to the other. The output signals from these channels are passed through the phase splitters 96 and 97 'so as to form four square wave signals lying in a phase square. These four signals are the four pulses which are used as preparation or transmission or control pulses for the switching tubes 81-84. In addition to the reproduced signal from the respective output head, they are applied to the control grid. When displaying a television signal message, it is desirable to use a blanking switch in conjunction with the switch to provide the timing information used to place the switching operation in the horizontal blanking interval.

12 shows a block diagram of a suitable blanking switch. The composite, reproduced video signal is fed to an amplifier 101 and a limiter 102 , the output signal of which is used to block a multivibrator 103 which oscillates freely at 15.75 IcHz. The rear edge of the multivibrator pulse controls the switching time. In the case of the multivibrator, a variable control is provided so that the switching time or switching cycle can be set within the rear black switch. The square wave signal at the multivibrator 10,3 is differentiated by the differentiator 104 , clipped and amplified by the amplifier 106 in accordance with the trailing edge of the square wave to produce a sharp pulse. In the same case, the 480 Hz key signal from the switch is limited, amplified by the amplifier 107 and applied to the phase splitter 108 . The output of the phase splitter is applied to amplifier 109 , where it is amplified and applied to another phase divider 111 . The 15.75 kHz pulse waves are added to the output signals of the phase splitter via resistors 112 and 113. The sum signal is then clipped by limiters 114 and 116 and applied to a multivibrator 117 which forms an output signal in the form of a square wave. The multivibrator is triggered in such a way that the pulses

ίο only let the multivibrator jump into one polarity from the upper channel, while the impulses from the lower channel cause it to jump into the opposite polarity. The first impulse that occurs in each group causes the multivibrator to jump. Both edges of the square wave output signal correspond in time to the rear black switch of the video blanking interval. The output of the multivibrator 117 is applied to the simultaneously limiting amplifier 89 in order to stimulate the switching time so that the switching process takes place during the horizontal return of a video signal.

As already described, the output of the switch is applied to the demodulator 76, which is used for this

serves to form a demodulated, composite signal. When a television signal is reproduced, the demodulated signal is applied to a working amplifier 77 . The working amplifier is designed in such a way that it makes the final output of the reproduced signal usable for transmission by radio or other transmission. Its main purpose is to remove any objectionable protrusion from the blanking and sync pulses or the area between them, as well as to limit any noise to certain peaks during the frame interval. The working amplifier also provides a means for correcting video linearity and for local or remote control of both the video and sync signal levels.

As already mentioned, the position of the curved tape guide 21 determines the pressure between the rotating heads and the tape. It is important that the pressure during reproduction be adjusted so that no timing error or timing error occurs in the reproduced signal. This is achieved through a tape guide servo system. Such a servo system mainly includes a compensation sensor 78, which generates an error signal for the control device 79, which can be set both for manual control and also for automatic control of the tape guide. The output of the control device is fed to the amplifier 80, which feeds the tape guide drive .85. The tape guide drive drives the guide 21 to control the pressure between the tape and the heads. When playing a television program, the compensation sensor 78 responds to errors that occur when the time span between the leading edges of two horizontal synchronizing pulses, which occur shortly before and shortly after a head switch, is different from the average time between the leading edges of the synchronizing pulses during the time in which a head carries out the brushing. The compensation sensor receives the horizontal synchronization pulses from the output of the working amplifier 77 as well as the 480 Hz control pulses from the switch 61.

9 10

The rotary head assembly, the guide, the drive shaft 162 supported bearing 161. An arm 163 is

and the associated parts are attached in detail at one end to the shaft 162,

the F i g. 4 to 10 shown. The head assembly while its other end is arranged so that

comprises, as already mentioned, several head units it touches an adjustable stop screw 164,

16, which are attached to the circumference of a head drum 18, 5 which are attached to the actuating arm 166 of the tape guide

crdnet are. Drive is carried along one side of the head assembly.

is a tape guide 21, which the tape in front of a suitable drive device, such as. B. one of the rotary head arrangement holds in a curved shape. A rotary electromagnet 167 is attached below the base base plate 130 carries the moving parts and plate 130; its shaft is with the shaft can be on the cover plate or the control panel 192 io 162, which is mounted in the base plate and on the one of a complete machine. eccentric pin 168 is attached, coupled.

The rotary head assembly 12 is connected to slip rings. When the electromagnet 167 is excited, 29 is connected, so that the tape guide 21 labeled 1 to 4 is in its advanced position, each with a terminal of the head winding, and the arm 163 is located Establish the connection against the stop lashings. The conductor 5 and 15 screw 164. If the electromagnet 167 is not the associated slip ring is energized as a ground connection, as is e.g. B. for tape rewinding of the trained. The inner or rotatable part is the case, the arm 163 around a limited slip ring arrangement can be rotated counterclockwise to a kind of star 134 amount as attached and this is fixed by screws 137 as shown in FIG. 7 is shown so that the eccentricity with the head drum 18 and a drive hub ao between the shafts 162 and 168 clamped a displacement 136 of the motor shaft. A part of the arm 163 caused and the guide for the purpose of the head circumference can be retracted by a housing 138 of free mobility of the band, which is carried by the base plate 130 , the guide 21 is together with the arm 146 . The adjacent housing parts 139 can be removed from the machine, so operated to serve the photoelectric tube or photo 25 the operator the lever 151 to compress the spring cell 42 and the lamp 41 together with equipment 152 and the roller 154 from the lines to focus this on the circumference of the cam surface 156 to make free. Then the ring or the washer 39 on the hub 136 to arm 146 along with the guide can be removed and encompassed. As already mentioned, the.

a part of the circumference be blackened while the 30 It is desirable for the arm 146 by Hilfsvorrich-

The remainder is designed to be light-reflecting, so that it can be secured with lines near its free end,

switch connected to the photoelectric tube. It is also desirable to have a device for setting

serves to provide square wave pulses in synchronism with len the height of the guide member to the

to generate the head circulation. These pulses are used to control the height of the arm 146 . This is

then, as already described, a slide 171 in one in the base plate 130 for the control and 35

Synchronization of the motor used. formed fitting slot provided. The sledge is

The tape guide 21 has a curved inner with its one end by means of a bolt 172 on

surface 144, which includes part of the head circumference. attached to the base plate. The other end is a

It is attached to an arm 146 which is adjustable above the base plate 130 by means of a bolt

Base plate 130 is and one end of which is releasably fastened 40 174 , which has a differential thread arrangement

is attached to a pivot pin 147 . The one used to adjust the height of this end of the carriage

Pivot pin 147 is held by a retainer. A vertical movement of the slide is used

148 and is, as can be seen, with the help of a vertical adjustment of the arm resting on it

146. "Teflon" inserts 176 (Fig. 8) attached to the arm

brings. The guide part 21 as well as the arm 146 are 45 slides are attached, are used to create smooth,

movable between limit positions; in one of the low-friction bearings on which the arm rests

this is the guide member of the head assembly can move.

withdrawn so that the tape is free on the guide. The curved surface 144 of the guide member 21

Guide device can pass without of the is preferably with an arrangement of grooves

Head units being touched; in the other is 50 or recesses, as shown in Fig. 4,

the tape advanced towards the head so that you can see. So is a groove 177 in one of the rotation

it in pressure contact with the head units 16, the level of the head unit 16 corresponding level.

carried by the head drum 18, held formed. Further grooves are in the neighborhood

will. provided on both sides of the groove 177 to the

Means are provided by which the 55 flexible conduit 179 can be connected to a suction air duct 21 normally against the head assembly source. Which is pressed during the. A lever 151 is under pressure from normal operation, ie when recording and / of a spring 152 and is used by a pivot pin or reproducing operations applied suction attached to the base plate 130 153rd A roller 154 for holding the outside of the belt intimately is carried by one end of the lever and 60 in contact with the guide surface. As in Fig. 7 an inclined cam surface 156 touches it, which is placed on the projection 157 of the arm 146 is formed at the lower end of the guide part 21. Provided by means of an abutment 191; this is used to operate the cam surface 156 and the roller 154 is used to touch a strip edge. It is in this Ausfüh-Kraft of the spring 152 normally to the Arm approximately example assumed that the head and the guide resiliently press against the head and 65 counterclockwise direction of rotation as shown down against the base plate 130 . in Fig. 7 moves.

An air cooling system for the motor is attached to the projection 157 of the arm 146.

Fixed stop screw 158 touches one of the treatment to be provided. To this end, an air line connects

11 12

182 to generate the motor housing 183 and a suitable suction error signal which is used to control the air source so that cooling air is constantly used by the motor pressure between the tape and the head. The windings are sucked. It is also desirable to provide an error signal from the reproduced remote pneumatic dust extractor by sensing the timing offset from the tape as well as from the vicinity of the timing error caused by improper turret units. For this purpose adjustment of the tape guide is caused. In the case of the housing part 138 designed to be hollow and connected by the reproduction of a television message, the similar suction air line 184 is connected, so that this means on the error that occurs when the time constantly air from the area of contact between the front edge of two horizontal heads and Sucked off tape and in this way io tal synchronization pulses, which occur immediately before dust and other small foreign objects from the working area and immediately after switching, are removed from the processing area. The operation of a magnetic tape recorder of the type shown at the front edges of the synchronization pulses is as follows: During normal recording, during the time when a head crosses the drawing and / or playback operation, the tape is stroked . On the transverse tracks, a leadership can be advanced towards the head; their precise control signal is recorded, and the playback position in this embodiment is used by to form an error signal,
the facilities described in more detail here, such as FIG. 14 shows, synchronizing pulses are correct, which are used for the automatic control of the position from the working amplifier to the amplifier diffusion of the arm 163 . This setting is 20 rentiator 211 placed, formed which trigger pulses for controlling the contact pressure between the band and these pulses are applied to the monostable Multivi-head units in order, as already mentioned, set clock error to Brator 212 einkompensieren during normal operation so on. When the tape is transported and returned, the electromagnet 167 is de-energized so that it generates a pulse of about 57.5 misc. Since the horizontal that the guide part is retracted and the 25 sync pulses can move freely a distance of 63.5 Mi-band. microseconds, there is a 6 microsecond. In FIGS. 5, 7, 9 and 10, a suitable interval between the point in time when the position of the guide can be adjusted is shown. the multivibrator returns to its stable state - the adjustment device for the guide is at the time of the return and the point in time where it is fixed by a base plate 192 through a bracket 190. 30 trigger pulse from the multivibrator 212 again. For example, the console 190 can be triggered with screws. In Fig. 13 A are the horizontal ones

193 be attached to the plate 192 . Shown at the bottom of synchronizing pulses, while the on-off end of the console there is disposed a motor 194 so _gan g of the multivibrator occurring waveform at that its shaft extends upward. The engine 14 β is shown. The pulse 213 is a negative one

194 can be an eddy current motor that only produces 35 pulses with a duration of 6 microseconds.
runs when voltages with different phases These pulses are applied to a sawtooth generator on its two windings. A 214 set, the normally a highly conductive is always present as _an d switched off by the negative pulse 213 that the startup of the engine may include the switching on of the tube when the apparatus. When the tube is switched off voltage depends on the other phase. 40, the anode voltage rises rapidly to the value

The motor 194 is used to drive the spur gear of the anode supply voltage. The one attached to this tube

196, the closed circuits with the spur gear 197 on the setting are designed so that

screw 198 is engaged. The adjusting _{screw em} condenser at a speed of about

198 is stored with its thread in the console part 199. 11.5 V is charged per microsecond. So will

When it is rotated, it pushes the time or the clock of the negative pulse 213 depending on the rotation

direction the cone 201 upwards or downwards. changes, the capacitor charges on you

The cone 201 contacts a value higher or lower than the normal value on the operating arm

166 attached pin 202. The arm 166 is pivoted to which it is in an interval of 6 micro-

bar held by a pin 203 and stretches reached seconds. For example, an error results

upwards, so that its upper end 204 next to the 50 of 1 microsecond at the distance of the synchronizing

Arm 163 lies. The upper end of the actuating arm pulses, which start the multivbrator, a

166 carries the adjustment screw 164. Thus causes a time change that is 1 microsecond greater or

Forward or reverse rotation of the motor one lift is less than the normal, 6 microseconds

or lowering the cone 201, causing the arm 166 to decrease in time. This means in the above-mentioned

pivoted and the arm 163 inward or outward 55 charging speed a peak voltage difference

is pressed to reduce the pressure between the solenoid of the signal of 11.5 V.

and the rotating head units. The tips are used to create an RC circuit

place. to charge to its peak. The circle becomes like this

A variable resistor or a potentio- adjusted that its voltage in an interval

Meter 206 with its shaft 207 to the motor 60 _V on 60 microseconds drops by about 7 V. on

shaft 208 connected by a coupling 209 . The this way becomes a 7V sawtooth wave of

Rotation of the motor is used to turn the grinding tip to tip formed. The sawtooth shape is in

contact of the potentiometer 206, shown in this way Fig. 13C. Here you can see that the

to cause a change in resistance. The Kon sawtooth fluctuates around a reference level 216. Of the

sole 190 can also be suitable terminal blocks 210 65 crossing point of the sloping flanks 217 of the

wear. Sawtooth shape is used for precise timing

As already mentioned, a sensor works in a predetermined time after the tip of the sawtooth bond with the tape guide control to turn a shaft. Such a point exists at around 80

microseconds behind the head switching time t _v (FIG. 13). This point in time is defined by the leading edge of the 480 Hz switching pulse 217. If an error occurs, the point in time t ₂ comes to lie somewhat before or after the normal point in time and enables the circuit to charge itself to a higher or lower value. The waveform at time t _% gives an error voltage if the trigger time did not occur at the correct instant. For example, in Fig. 13C, if the horizontal sync pulse 218 occurs later than normal, the sawtooth waveform does not cross the zero line at time t _v as indicated by the dashed line for normal timing. The waveform has a positive voltage, as indicated at time t _s. If the sawtooth waveform is measured at this point, the output voltage will be positive. Similarly, if the horizontal sync pulse 218 occurs earlier than normal time, a negative output voltage results; the negative output voltage is indicated by the dashed line 221 , which is then obtained when the waveform is measured.

The measurement signal must therefore be related in time to the leading edge of the 480 Hz switching pulse, which defines the point in time t _±. The 480 Hz switch pulse is applied to an amplifier differentiator which amplifies and differentiates the pulse to apply a series of positive trigger pulses to the phantastron delay circuit 223 . The phantastron delay circuit provides an output voltage pulse 224, the width of which is controllable. The trailing edge of the pulse 224 (FIGS. 14 and 13E) defines the measurement time t ₃ .

The output of the Phantastron is applied to an amplifier 226 , the output of which is connected to the primary winding of the transformer 228 by a capacitive coupling 227. Positive and negative peaks as shown in FIG. 13 F and 14 are denoted by 229 , appear on the secondary winding of the transformer. The first peak corresponds to the leading edge of the phantastron pulse and has an effect on the measuring circuit 231. The measuring circuit 231 comprises four diodes arranged as a bridge circuit. The polarity of the negative tip is such that none of the diodes is conductive. However, during the positive peak that occurs at the time t _s at the end of the phantastron pulse, the diodes forming the bridge circuit 231 conduct across both branches of the circuit and allow the capacitor 232 to be charged. The voltage across this capacitor builds up to the maximum value of Voltage spike and creates a counter voltage for the diode bridge during the pulse-free time. Due to this counter voltage, the signal wave occurring at the upper end of the bridge on line 233 is completely separated from the other bridge branches during the pulse-free interval, the only requirement being that the voltage wave does not exceed the value of the counter voltage at this point. During the interval of the second peak 229, the circuit acts like a closed switch, allowing the capacitor 232 to be charged through the tip and to allow the capacitor 234 to be charged up to the measured voltage from the sawtooth wave. The voltage appearing on capacitor 234 is the sought error signal that is required to operate the tape guide amplifier. Potentiometer 236 allows adjustment of the level of the error signal applied to the tape guide amplifier.
Noise pulses can cause large positive voltage spikes to appear on line 233. If these peaks exist, they exceed the counter voltage of the measuring circuit and produce an erroneous fluctuation in the error signal. To this

To prevent this, a crystal diode 238 can be provided to limit the waveform to about 10 volts, an amount well within the limits of the reverse voltage.
The error signal developed by the circuit is integrated over a significant number of cycles or oscillations and is not influenced by the random noise in the reproduced signal. However, if the picture is deteriorated, for example if the signal from one of the

so playback heads, or when the video signal stops, so facilities can be provided to control the tape guide from the automatic Switch operation to manual operation.

A protective relay 241 in conjunction with a triode amplifier 242 can be used for this purpose. When a normal signal appears on line 233 , the combination of diode 243 and the AC circuit with resistor 244 and capacitor 246 develops a negative bias on the grid of tube 242. A few thousandths of the current have the opportunity to flow via a coil 247 of the differential relay, which also has a coil 248 . By adjusting the current through the counter coil 248 with the potentiometer 249 , the relay can be adjusted so that it remains open and allows the automatic operation of the tape guide system while the relay is open. If the video signal fails completely, no signal appears on line 233 , the bias voltage on tube 242 becomes zero and allows more current to flow in the relay. The relay 242 is then closed in one direction and causes the system to be switched to manual mode. On the other hand, if the signal contains excessive noise and excessive negative spikes appear on line 233 , this will bias tube 242, reducing the current through coil 247 and closing the relay in the opposite direction; This also switches the device to manual mode.

The output error signal, which occurs at the variable tap of the potentiometer 236 , is carried via the line 251 to the contacts 252 and 253 of a relay. In the illustration in the drawing (Fig. 14) the relay is in the position for manual operation. When the moving contacts 254 and 256 are brought to their upper position, the amplifier 257 is switched so that it picks up this output error signal.

The amplifier 257 is used to generate a signal for one of the windings of the motor 194. When the output voltage of the line 251 has one polarity, the amplifier produces an output signal which is in phase with the signal applied to the other winding of the motor so that the motor 194 starts up in one direction of rotation. If the polarity of the error signal on line 251 is reversed,

so the amplifier 257 generates a signal of opposite phase which the motor 194 in opposite Start direction, lets. In the state of equilibrium, i.e. That is, if on line 251 no Input is applied, the output of the amplifier is such that the motor 194 is at a standstill remains.

As already mentioned, the rotation of the motor 194 is used to adjust the tape guide so that timing errors are corrected the position of the various relays, as indicated in the drawing (Fig. 14), becomes an input signal for the amplifier from the voltage divider comprising resistors 262, 263 and 264, taken. The resistor 263 is connected as a potentiometer, so that that which occurs on the line 266 Voltage can be changed. At the top of the resistor is a positive and an the lower end is applied a negative voltage so that the output of line 266 is at zero positive or negative values can be set. The voltage on line 266 is applied to the Terminal 267 applied. The voltage on line 268 is fed to relay terminal 269. the The voltage on line 268 is that occurring at variable tap 271 of potentiometer 272 Tension; the potentiometer is connected to the same voltage sources. The arm 271 is driven by motor 194. Thus, the variable tap becomes with manual adjustment 273 of the potentiometer 263 adjusted by hand; the motor is used to move the tap automatically 271 to restore equilibrium. When the engine is running, it stops the '21 guide.

The method of operation can be illustrated using the block diagram in FIG. 3 still explain Mater. the Resistors 263 and 272 are shown as being in a bridge circuit with both of them Terminals positive and negative voltages are applied. The changeable gripper 273 is with the Resistor 263 and the variable tap 271 connected to resistor 272. Thus is located by adjusting the tap 273 by hand, the bridge becomes unbalanced; it becomes through the Belt guide drive brought into equilibrium; the motor serves as the belt guide drive 194, which drives the potentiometer arm. The switching arm 274 is in this example in the lower position, where he applies the signal to the amplifier 257, as already mentioned. If the Arm 274 is in the upper position, it is connected to the sensor unit, which sends the error signal generated to move the tape guide automatically.

Like F i g. 14 shows, the device can be brought into the position for manual control by the Switching contact 278 is set so that it closes the line 279. If the line is open, it is located the circuit is in the automatic mode and the light 281 indicates that the circuit is set to automatic compensation.

Note that automatic compensation is only used during playback. In summary it should be said that with manual operation the tape guide setting can be changed by changing the Potentiometer tap 273 is controlled. This potentiometer is a branch of one in itself Equilibrium circuit, the other branch of which is that driven by motor 194 Potentiometer is. A change in the de position; Control creates an imbalance in the bridge and the motor restores the bridge balance and makes a new setting the tape guide.

In the case of automatic operation, the position of the tape guide is determined by the output of the sensor for you automatic compensation controlled. The unit feels clock skew errors in the reproduced

ίο emitted signal caused by an imprecise tape guide setting are caused. The error voltage has the form of a direct voltage, whose amplitude and polarity are direct functions of the The amount and direction of the clock skew error in the signal. When applied to the Tape leader amplifier causes this error signal that the motor runs to the tape leader position to correct.

In Fig. 15 is a complete circuit diagram of the

ao feeler shown. The synchronizing pulses are applied to the grid of the tube 280, which acts as an amplifier works. The pulses are differentiated by capacitor 282 and resistor 283 to Provide trigger pulses for the monostable multivibrator containing the tube 284. The diode 286 is used to remove the negative parts of the differentiated waveform. The ones on the grid of the Trigger pulses applied to triode 287 of the monostable multivibrator are positive peaks which correspond to the leading edge of the horizontal synchronizing pulses.

The multivibrator is set during normal operation to give pulses of 57.5 microseconds Duration generated. Because the horizontal sync pulses are 63.5 microseconds apart there is 6 microseconds between the time the multivibrator tips over and the time it does is triggered again. As a result, a waveform of the type shown in Fig. 13B occurs the anode of the tube section 288 in appearance. This pulse is applied to the grid of tube 289, which is biased to be highly conductive; its anode is held at about 50 volts. For the 6 microsecond interval between the pulses, the tube is switched off so that the capacitor 291 is charged via the resistor 292. The ÄC constant of the capacitor 291 and resistor 292 is chosen so that at the end of the 6 microsecond pulse this has as steep a slope as possible, namely a charge rate of approximately 11.5 V per Microsecond. At the end of the 6 microsecond pulse, the tube becomes conductive again to the capacitor to discharge quickly. The result is a series of pulses or peaks that appear on the horizontal Line occur whose amplitude is constant from peak to peak, provided that the time span remains constant between the leading edges of the horizontal pulses.

If the tape guide is poorly adjusted, so that a time error of 0.1 microseconds when switching of the heads is created, this causes a 0.1 microsecond change in the sawtooth charge time. Since the tip of the sawtooth has a charge edge of 0.5 volts per microsecond, one occurs Amplitude change on the order of IV each time a head is switched am top of the tip.

The tips are connected to a resistor via a diode 296

Capacitor 297 placed. This capacitor is charged to the peak of each sawtooth pulse 294. Resistor 298 allows the charge to drop at a rate of about 7 volts during one line interval. This way the tops of the tips are retained. The impedance of the cathode of tube 296 is so high that a cathode amplifier 299 is used to isolate the circuit and provide a low impedance output of the sawtooth tips as indicated at 301. The capacitor 302 , together with the inductance 303, forms a high-pass filter to eliminate the lower frequencies introduced by the previous circuit.

As noted, it is desirable to measure or sample the waveform appearing on line 304 at some point after the beginning of a horizontal sync pulse in order to produce an error signal of correct polarity. For this purpose, the 480 Hz switching signal is applied to the grid of the tube 311 , which is connected as an amplifier. The amplified signal is differentiated by the combination of the capacitor 312 and the resistor 313. Diode 314 is used to clip negative spikes so that only positive trigger pulses are applied to the phantastron delay circuit with tube 316 . The output of the Phantastron results in positive pulses of approximately 75 V, the width of which is controlled by means of the 317 potentiometer. The rear edges of these pulses determine the measuring time t ₃ .

The output from the Phantastron is applied to an amplifier with the tube 318 , which is used to separate the measuring or test circuit. The transformer separates the previously described diode clamping circuit from earth and differentiates the square wave input. The mode of operation of the measuring circuit 231 as a switch as a function of pulses applied thereto from the phantastron circuit has already been described. Circuit 231 is used to switch capacitor 234 so that it is charged by the error signal appearing on line 304. The circle causes the measurement or investigation of the sawtooth voltage, which is derived from the synchronizing pulses at a specific point in time, in order to derive an error signal therefrom if clock shift errors are present.

A sensor was built for automatic compensation according to the above information, the various components of which had the following data:

Voltage + V.
Tubes

+ 250V

281 V ₂ 12AT7

286 V ₂ 6AL5

288 12AU7

289 V ₂ 5687

296 V ₂ 6AL5

299 V ₂ 5687

311 V ₂ 12AU7

316 6AS6

318 V212AU7

55

60

65

236 50 kilo ohms

244 330 kilo ohms

249 147 kilo ohms

283 10 kilo ohms

292 5 kilo ohms

298 22 megohms

313 47 kilo ohms

317 25 kilo ohms

322 100 kilo ohms

323 150 ohms

324 10 kilo ohms

326 100 kilo ohms

327 5 kilo ohms

328 8200 ohms

329 100 kilo ohms

331 10 kilo ohms

332 10 kilo ohms

333 3300 ohms

334 10 megohms

336 470 kohms

337,470 kilo ohms

338 1 megohm

339 27 kilo ohms

341 68 kilo ohms

342 1800 ohms

343 270 kilo ohms

344 10 kilo ohms

346 1 kilo ohms

347 470 kohms

348 1 megohm

349 39 kilohms

351 820 ohms

352 8200 ohms

353 6.8 kilo ohms

354 33 kilo ohms

356 4.7 kilo ohms

357 6800 ohms

358 470 KüoOhm

359 1200 ohms

361 4.7 megohms

362 2700 ohms

363 330 ohms

364 22 kilo ohms

Capacitors

227 800 pF

232 0.01 μΡ

234 0.47 μΡ

246 8 μΡ

282 27 pF

291 0.002 µΡ

297
302
312
366
367
368

100 pF
0.22
27 pF
10 HF
47 pF
4OpF

369 500 pF

371
373 374 376 377 378 379 381

10 µ
1.0 μΡ
0.001
10 μΡ
0.001
0.01 µ
0.01 µ
0.002

Crystal diodes

243 1N279

314 1N279

382 1N432

383 1N68A

384 1N68A

386 1N432

387 1N432

388 1N432 ίο

389 1N432

Coil 391 100 millihenry

A sensor built according to the above information was able to detect small clock shift errors up to 0.05 microseconds and compensation voltages of a magnitude of 0.25 V to deliver. A complete recording and reproducing system was constructed according to the above Details carried out and used to record a monochrome television program. The effect of timing errors on the reproduced signal was negligible.

As stated above, the control system for the tape guide during playback can also can be used when reproducing signals other than television signals. A recorded signal which contains signal parts with a known frequency separation can to the feeler of FIG. 3 can be created. The sensor is used to generate an error signal that depends on the known frequency error (clock skew error) in the reproduced signal is. For example, a standard frequency can be superimposed on and along with the signaling message to be recorded. When playing, this signal can be used as the reference frequency in the same Act like the horizontal synchronizing pulses in the described system as a reference frequency works. The operation of the automatic compensation system in other respects is similar as described above.

There has thus been provided an improved recording and reproducing apparatus. A servo system automatically adjusts the pressure between the tape and the head units depending on one Error signal derived from the reproduced signal. The control of the pressure is used for the automatic correction of clock shift errors resulting from changes in the pressure between head and tape as a result of errors in the setting of the tape guide device, the tape tension and the like can occur.

Claims (5)

Patent claims: 1. Magnetic tape recorder for recording and / or playback of broadband signals, especially television signals, in the form of consecutive, across or diagonally across the magnetic tape running track parts, the arrangement of a rotary head with multiple head units magnetically recorded or scanned, using a the magnetic tape before the rotary head assembly in a curved shape leading tape guide, thereby characterized in that the tape guide device (21) for controlling the contact pressure between the magnetic tape (11) and the Head units (16) arranged to be movable in the direction of their distance from the rotary head arrangement (18) and through devices (78, 79, 85 or 146 ff, 194 ff., 211 ff.) depending on one error signal derived from any phase errors in the signal during playback can be controlled in this way is that the phase errors are each caused by changing the contact pressure between the Magnetic tape (11) and the head units (16) are corrected. 2. Magnetic tape device according to claim 1, characterized by a running magnetic tape by vacuum (suction air) holding tape guide device, in which the negative pressure in Can be controlled as a function of the error signal. 3. Magnetic tape device according to claim 1 or 2, characterized by one for forming the Error signal as a function of occurring between predetermined horizontal sync pulses Device serving clock errors. 4. Magnetic tape device according to claim 3, characterized in that the horizontal sync pulses Recording device for forming an output signal which fluctuates around a reference level is used, from which periodically by a test device for the purpose of forming the phase errors error signal proportional between the predetermined horizontal sync pulses a sample is taken at a time. 5. Magnetic tape device according to claim 4, characterized in that the periodic removal Test device each serving a sample depending on the switch of the head units when assembling the overall signal to be reproduced Switching pulses is controllable. Documents considered: German Auslegeschrift No. 1049 904; German patent specification No. 1014153. In addition 3 sheets of drawings 609 588/273 6.66 © Bundesdruckerei Berlin