JPS5922253A - Automatic switching device of speed of magnetic tape - Google Patents

Abstract

PURPOSE:To switch automatically and continuously the speed of a magnetic tape to the one corresponding to a recording mode, by detecting the angular speed of a feeding side reel board and a rewinding side reel board at the reproducing of a control pulse recorded in the magnetic tape, and executing arithmetic the magnetic tape distance between the control pulses. CONSTITUTION:The 1st angular speed detector 24 measures the pulse interval of the 1st pulse P1 train at the reception of a control pulse CTL and fixes the reciprocal number of the measured value as the 1st angle omega1, and the 2nd angular speed detector 25 detects the 2nd angular speed omega2 from the 2nd pulse P2 train and outputs the detected value to an operating circuit 27 for winding tape length. The operating circuit 27 finds out the length of the winding tape of a feeding reel 17a from the 1st and 2nd angular speeds omega1, omega2 and outputs the operated values to a magnetic tape distance arithmetic circuit 28 successively. The operating circuit 28 finds out the distance of the magnetic tape put between the two control pulses CTL and outputs the results to a comparator 29 successively. The comparator 29 compares data set up in accordance with the recording mode of an ROM 30 with the magnetic tape distance to control a mode switch 8.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an automatic magnetic tape speed switching device, and particularly to a magnetic tape speed automatic switching device that detects a control pulse indicating the position of a recording track and automatically switches the magnetic tape speed during playback. The present invention relates to an automatic magnetic tape speed switching device.

[Technical background of the invention]

In a magnetic recording/reproducing apparatus, a control pulse CTL is recorded on a control track 2 of a magnetic tape 1 shown in FIG. 1 to indicate the position of a recording track. The recording speed varies depending on the recording mode.

Hereinafter, for the sake of explanation, we will assume that the data was recorded at two speeds: β■ mode (2, OO, referred to as the first mode) and β■ mode (1,33 (, ψ, referred to as the second mode). do.

The control pulse CTL1 is reproduced by the control head 3 and sent to the first mode period determination circuit 5 and the second mode period determination circuit 6. First mode period determination circuit 5
outputs an L level signal when it is lower than the comparison signal f (frequency is 27 By), and outputs an H level signal in other cases. The second mode period discrimination circuit 6 compares the comparison signal f (frequency is 37 Hz) and outputs a signal at L level if the frequency is high, and an I (level) signal in other cases. A mode switching signal is outputted to the bins 7a and 7b, and a mode switching signal is outputted from the bin 7c to the mode switching device 8.On the other hand, a mode switching signal is outputted from the capstan flywheel 9 to the head 1.
The rotation signal Fo taken out at 0 is frequency-divided by the frequency division ratio determined by the first mode frequency divider 11 and the second mode frequency divider 12, and becomes a constant frequency. The rotation signal FG converted to a constant frequency is used as an input signal of the capstan AFC1-3, and an output signal is fed back to the capstan motor 14.

Therefore, the running speed of the magnetic tape 1 is 2.0 in the first mode.
00M less, and is maintained at 133M less in the second mode.

[Problems with background technology]

The playback modes include trick playback, ie, slow playback, in which the running speed of the magnetic tape 1 does not correspond to the first mode or second mode during recording. The recording mode cannot be identified unless the running speed of the magnetic tape 20 at the time of trick playback is close to 2.00 crrV'+D or 1.33 C7n7. Therefore, when entering trick play,
The trick reproduction signal is input to the bin 7a of the RS flip-flop 7 through the bin 16 and the diode 15 (r) so that the state of the RS flip-flop 7 does not change. Control, for example, setting the voltage applied to the cab stan motor during intermittent slotting,
It is not possible to switch the hiteo signal characteristics, etc. Further, when recording is performed in a different recording mode, the operation of the mode switch 8 is locked by the trick playback signal and cannot be changed, which may result in abnormal operation. Furthermore, at the start of recording mode determination, the running speed of the magnetic tape 1 cannot be determined until the AFC control is initiated by the capstan AFC 13, which causes instability in lighting and extinguishing of recording mode indicator lamps, etc., resulting in malfunctions. Sometimes.

[Purpose of the invention]

An object of the present invention is to detect all the angular velocities of the supply reel table and take-up reel table at the time when the control pulses recorded on the magnetic tape are reproduced, and to calculate the magnetic tape distance between the control pulses on the magnetic tape from this angular velocity. An object of the present invention is to provide an automatic magnetic tape speed switching device which can always automatically switch speeds in accordance with recording modes by calculating .

[Summary of the invention]

The present invention is configured to determine the recording mode immediately upon reproducing control pulses recorded on the magnetic tape, and to switch the magnetic tape speed in accordance with the determined recording mode. At the first point in time when the control pulse is regenerated, the angular velocity of the supply reel base is detected from the first pulse train generated by the rotation of the supply reel base, and in the same manner, the angular velocity of the take-up reel base is detected from the second pulse train. It is designed to detect angular velocity. If the two angular velocities are known, the length of the take-up tape on the supply reel stand (and the take-up reel stand) at the first point in time can be calculated. Therefore, by calculating the length of the wound tape at the second point in time when the next control pulse is reproduced, the distance of the magnetic tape between two control pulses can be obtained. Since the distance of this magnetic tape is constant in all parts unless the recording mode changes, the recording mode is determined by comparing it with fixed data stored in the storage device in advance.

[Embodiments of the invention]

Hereinafter, one embodiment of the magnetic tape speed automatic switching device according to the present invention will be described in detail with reference to the drawings.

Components that are the same in FIG. 2 and FIG. 1 are designated by the same reference numerals, so their explanation will be omitted.

In FIG. 2, 17 is a cassette, and the supply reel 1
The take-up reel 7a and the take-up reel 17b are placed on a supply reel stand 18 and a take-up reel stand 19, respectively.

The rotation of the supply side reel stand 18 and the take-up side reel stand 19 is transmitted to the first angular velocity detector 24 and the second angular velocity detector 25 through the reel pulse sensors 20, 21 and amplifiers 22 and 23, respectively, by a first pulse P+ and a first pulse P+. It is applied as a train of two pulses P.

The control pulse sending circuit 26 receives control pulses CTL recorded on the magnetic tape 11C via the control head 3. This control pulse CTL is shaped and supplied as a timing pulse to the first angular velocity detector 24, the second angular velocity detector 25, and the winding tape length calculation circuit 28.

The first angular velocity detector 24 measures the pulse interval of the train of first pulses P at the time of receiving the control pulse CTL. The reciprocal of the measured value is output to the winding tape length calculation circuit 27 as the first angular velocity ω1.

The second angular velocity detector 24 uses the control pulse CT
At the time when L is received, the second angular velocity ω2 is similarly obtained from the train of the second pulse P2 and outputted to the winding tape length calculation circuit 27.

The winding tape length calculation circuit 27 receives the control pulse CTL as a timing pulse, and each time calculates the length of the winding tape of the supply reel 17a using the first angular velocity ω1 and the second angular velocity ω. The obtained numerical values are sequentially output to the magnetic tape distance calculation circuit 28.

The magnetic tape distance calculation circuit 28 uses a control pulse CT.
Two control pulses CTL are generated from the numerical value of the length of the winding tape of the supply reel 17a, which is input sequentially according to L.
Calculate the distance of the magnetic tape narrowed to . The calculated magnetic tape distances are sequentially output to the comparator 29.

The ROM 30 stores data on the magnetic tape 1 relating to the first mode (2,00 MB) and the second mode (1,33 MB). The comparator 29 compares the data set corresponding to the recording mode of the ROM 30 and the magnetic tape distance. The mode switch 8 is controlled according to the comparison. Code 9 in the figure
3 is a capstan, and 9b is a pinch roller.

Next, the operation of the circuit will be explained.

When the control pulse CTL is sequentially reproduced at points t1 and 17 in FIG. 3(4), the control pulse sending circuit 26 outputs the shaped control pulse CTL at point b as shown in FIG. 3(B). Ru.

At the t'+ point, the first point of 0 shown in Figure 3 (C) and (B)
The first two of the pulse P+ and the second pulse P2 at point d
The first angular velocity ωl and the second angular velocity ω! are calculated as the reciprocals of the intervals between two pulses (indicated by diagonal lines). is output from the first angular velocity detector 24 and the second angular velocity detector 25. These measurements and calculations are performed at 17 points sequentially in response to the control pulse CTL. When the magnetic tape 1 is in the direction shown by the arrow, the interval between the pulses changes from small to small on the supply reel 17a, and from small to small on the take-up reel 171), and when the lengths of the respective winding tapes are equal, the measured pulses The mutual spacing will be equal. When the first angular velocity Cυ1 and the second angular velocity ω are known, the tape velocity V[ shown in the equation α1 in the table can be calculated. Further, by substituting the value of Equation 03 into Equation (9), the length L+ of the winding tip of the supply reel 17a can be obtained. The magnetic tape distance calculation circuit 28 sequentially calculates the value of the length L1 of the winding tape according to the formula (9) in the table obtained by calculation in the winding tape length calculation circuit 27.
Output to. The magnetic tape distance calculation circuit 28 subtracts the next input value from the previously input value of the length Ll of the winding tape to obtain the magnetic tape distance between the two control pulses CTL, which is then sent to the comparator 29. Send sequentially. The comparator 29 compares a plurality of fixed data relating to the recording mode of the ROM 30 with the input magnetic tape distance, and if they match, control corresponding to the determined recording mode is performed via the mode switch 8.

Since the fixed data in the ROM 30 has a certain margin of judgment, it is possible to prevent inability to make a judgment due to measurement errors and calculation errors.

In the above embodiment, two types of recording modes are used, but the present invention can also be applied to a case where a larger number of recording modes are set.

〔Effect of the invention〕

The magnetic tape speed automatic switching device according to the present invention detects the angular velocity of the supply side reel stand and the angular velocity of the take-up side reel stand.
a first calculating means that calculates the length of the winding tape of the supply reel from the two angular velocities; and a first calculation means that calculates the magnetic tape distance narrowed to two control pulses from the length of the winding tape. The structure is equipped with a second calculation means for storing fixed data for each recording mode, and a storage means for storing fixed data for each recording mode. It has the advantage of being able to perform calculations regardless of reversal. Therefore, even if the recording mode changes due to trick reproduction or the like, normal operation can be immediately continued. Furthermore, even in a transient state before being drawn into AFC control at the start of operation, the recording mode is immediately identified and the magnetic tape speed is switched, so there is no possibility that the display lamp or the like will blink due to malfunction.

[Brief explanation of the drawing]

FIG. 1 is a time chart of a conventional magnetic tape speed switching device as shown in FIG. Codes in the figure: 1 is a magnetic tape, 9 is a capstan flywheel, 9a is a capstan, 9b is a pinch roller, 1
7 is a cassette, 17a is a supply reel, 17b is a take-up reel, 18 is a supply side reel stand, 19 is a take-up side reel stand, 2
0.21 is a reel pulse sensor, 24 is a first angular velocity detector, 25 is a second angular velocity detector, 26 is a control pulse sending circuit, 2γ is a winding tape length calculation circuit, 28
is a magnetic tape distance calculation circuit, 29 is a comparator, 30 is RO
It is M.

Claims (1)

[Claims] In an automatic magnetic tape speed switching device that generates a first pulse train and a second pulse train according to the respective rotations of a supply reel stand and a take-up reel stand that run a magnetic tape on which control pulses have been recorded, the control a first angular velocity detection means for detecting the angular velocity of the supply reel stand from the interval between the pulses of the first pulse train at a first point in time when the pulses are reproduced; and from the interval between the pulses of the second pulse train. A second angular velocity detection means detects the angular velocity of the take-up reel stand, and a second angular velocity detection means detects the angular velocity of the supply reel at the first time point from the first and second angular velocities obtained by the first and second angular velocity detection means. a first calculating means for calculating the length of one winding tape; a second calculating means for calculating the distance of the magnetic tape between the first time point and the second time point by calculating the length of the wound tape; and a magnetic tape narrowed to two control pulses recorded on the magnetic tape. and storage means for storing fixed data related to the length of the tape for each recording mode, and the determination is made based on the magnetic tape distance between the first time point and the second time point obtained by the second calculation means and the fixed data. A magnetic tape speed automatic switching device 0 characterized in that the magnetic tape speed is changed according to the recording mode selected.