JPS58224453A - Circuit for detecting end of tape - Google Patents

Abstract

PURPOSE:To detect the end terminal of a magnetic tape simply and precisely, by detecting the noise of the travelling tape. CONSTITUTION:A reproduced output from a tape signal detecting circuit 5 is compared with a set reference value from the 1st reference voltage circuit 16 by a comparator 17, and when the output is less than the reference value, the reproduced output is discriminated as only travelling tape noise and a tape end terminal detecting output is generated from the circuit 17 to control a switching circuit 14, etc. Said configuration makes detection of the end terminal of the tape possible easily and presicely. In addition, a division between pieces of music is detected in the same manner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for detecting the end of a magnetic tape section in a magnetic recording/reproducing apparatus via a magnetic head.

Conventional means for detecting the end of a magnetic tape include mechanical means that detect the tape tension, methods that detect the stoppage of rotation of the reel stand, and electrical and optical means that detect the stoppage of rotation of the reel stand and counter using a leaf switch or hole switch. There are known methods that detect the end of the magnetic tape through a transparent leader tape section, and those that detect the end of the magnetic tape through a transparent leader tape section, in which a pair of light-emitting and light-receiving elements are arranged so that the magnetic tape is located in the middle. A leader tape section with a length of about 28 cm is provided at both ends of an ordinary C cassette magnetic tape. If this is converted into a travel time during magnetic recording and reproduction, it is approximately 6 seconds. The tape players currently available on the market as Quick Reverse are designed to shorten the round-trip travel time of the leader tape section to about 12 seconds, and there have been no other types of tape players that use optical means. Magnetic end detection means using optical means has a great advantage in its quick response speed, but on the other hand, it cannot be used with magnetic tapes having opaque leader tapes. Furthermore, the arrangement of each element and other parts regarding optical path setting becomes limited. Furthermore, it also has the disadvantage that it tends to be sensitive to bending of pacefill and peeling off of magnetic powder.

The present invention detects the running noise of the magnetic tape, regardless of whether the leader tape is transparent or opaque, eliminates the need for the troublesome process of setting the optical path, and solves the problem with an electric circuit that has a large degree of freedom in setting the additional parts. The present invention aims to provide a magnetic tape termination circuit. At the same time, the present invention is also intended to be used in conjunction with a song interval detection circuit.

Below, based on FIG. 1, noise in a magnetic recording/reproducing apparatus and magnetic tape, which are the basis of the present invention, will be explained. FIG. 1 shows an example of the noise spectrum of a magnetic recording/reproducing device. There is unavoidable noise in magnetic recording and reproducing devices including magnetic tapes. For example, bias noise, modulation noise,
Bulk erase noise, DC noise, beat noise, recording/playback noise, etc. Among these noises, recording/reproducing system noise is shown as device noise in band N1. Other noises are related to magnetic tape and are typical.
What is considered to be 1 is bulk erase noise shown in band N2 and bias noise shown in band N3. Other modulation noise, DC noise, and beat noise are added to device noise, bulk erase noise, and bias noise. Noise related to magnetic tape occurs only when the magnetic tape is in contact with a magnetic head and is running, and among the inevitable noises at the magnetic tape termination according to the present invention, only device noise is generated. will be detected.

In the example shown in Fig. 1, the device noise band N1 in the high and low frequency ranges has increased by -1, and the bulk erase noise band N2 and the bias noise band N2 have also increased.
3 is narrower. Therefore, when trying to detect these noises over all frequency bands, even if you try to detect whether the running of the magnetic tape has stopped or whether the running part has moved to the leader tape section, the difference in noise will be small. In some cases, the change may become indiscernible. In order to solve these considerations, the detection frequency band should be set to 2 KHz, which has relatively low device noise.
By detecting noise in the 5KHz band, it is possible to detect noise in the 5KHz band.
A difference of 0 dB can be found. The device noise N1 shown in FIG. 1 changes depending on the characteristics of the amplifier, and there are cases where the device noise does not increase even in the high frequency range, so there is no need to apply a high frequency filter.

The circuit of the present invention will be explained below using a block diagram based on FIG. An output signal from a magnetic head 4, which is a magnetic reproducing head that comes into contact with the magnetic tape 1 being run between the gap stun 2 and the pinch roller 3 and detects a magnetic signal, is amplified by an amplifier circuit 8. Since the amplifier circuit 8 amplifies the slight noise detected by the magnetic head 4, it is desirable that it be a low noise amplifier. The amplified output from the amplifier circuit 8 is input to the filter circuit 9, and as described above, a frequency band with small device noise is extracted. The filter circuit 9 may be provided before the amplifier circuit 8. The signal output via the amplifier circuit 8 and filter circuit 9 is rectified by a rectifier circuit 10.

Since the signal output by the rectifier circuit 10 is also unstable, it is averaged by a smoothing circuit 11. Although this smoothing circuit slightly impairs responsiveness, it reduces the hypersensitivity that is common with optical systems. In FIG. 2, the aforementioned amplifier circuit 8, filter circuit 9, rectifier circuit 10, and smoothing circuit 11 constitute the tape signal detection circuit 5. When the low-pass filter circuit 9 is provided between the amplifier circuit 8 and the magnetic head 4, the rectifier circuit 10 may be integrated within the amplifier circuit 8. The output signal of the tape signal detection circuit 5 is equal to the output voltage of the first reference voltage circuit 16, which is set to a voltage slightly higher than the output signal generated when the tape signal detection circuit 5 stops running the magnetic tape 1. If the output voltage of the tape signal detection circuit 5 becomes lower than the output voltage of the first reference voltage circuit 16 via the first comparison circuit 17,
(In other words, when the magnetic tape 1 stops running or runs through the leader tape section, the output signal of the tape signal detection circuit 5 shows the lowest value with a magnitude corresponding to the device noise.) The first comparison circuit 17 Generates an output signal. The switching circuit 14 is a circuit that enters a non-conducting state for a certain period of time when an operation signal (recording or playback operation signal) is input from the operation terminal C. This is to prevent movement. Therefore, the output signal of the first comparator circuit 17 after a certain period of time after the recording/playback operation is output to the terminal B. 6.

On the other hand, the output signal of the tape signal detection circuit 5 described above is
The level of the voltage is compared with the output voltage of the reference voltage circuit 18 through the second comparison circuit 19. Third reference voltage circuit 1
The output voltage of the magnetic tape 8 is set to be slightly larger than the maximum value of all noises (excluding noise during recording) accompanying the running of the magnetic tape 1. Therefore, it is higher than the set voltage of the first reference voltage circuit 16 described above. The second comparison circuit 19 detects that the output voltage of the tape signal detection circuit 5 is lower than the output voltage of the third reference voltage circuit 18, and outputs an activation signal. The integral time constant circuit 20 has a second
The comparison circuit 19 detects that the activation signal has been output for a certain period of time and outputs the activation signal. The switching circuit 21 is a switching circuit for a song interval detection operation, and is a switching circuit that becomes conductive when a song interval detection operation is performed and outputs to the output terminal A an activation signal of an integral time constant circuit that operates when a song interval is detected. (Currently, it naturally includes a switching circuit for detecting the intervals between a plurality of songs and selecting them.) Terminals indicate playback output terminals. Since many reproducing amplifiers are not used in common with the amplifier circuit 8 shown in FIG. 2, the reproducing amplifier may be provided in parallel with the amplifier circuit 8.

FIG. 3 shows another embodiment of the invention.

In FIG. 3, the same symbols as in FIG. 2 indicate circuits with the same names, and certain Q) indicate the same terminals.

As is well known, the output difference between the device noise shown in FIG. 1 and bulk erase noise and other tape running noises is minute, and as the tape running noise becomes smaller, detection becomes increasingly difficult. Therefore, an example of a circuit that can sufficiently handle even if the tape running noise is reduced by incorporating the division circuit 13 inside will be shown.

In FIG. 3, the tape signal detection circuit 5 includes the aforementioned amplifier circuit 8, filter circuit 9, rectifier circuit 10, smoothing circuit 11, as well as a second reference voltage circuit 12 and a division circuit 13. The reference voltage circuit 12 is a circuit that outputs a constant and stable voltage and forms the numerator in the division circuit. The output signal of the smoothing circuit 11 forms the denominator in the divider circuit, and the divider circuit 13 generates the maximum output signal when the magnetic tape 1 stops running. The amplifier circuit 8 used in FIG. 3 does not need to have a large amplification factor compared to the amplifier circuit 8 used in FIG. 2, so that the device noise can be reduced and stabilized. The output signal of the division circuit 13 is input to the tape end detection circuit 6 and the song interval detection circuit 7. Symbol 15 and symbol 22 are the first and second Schmitt circuits that operate above a certain voltage, and in the case of FIG.
The second Schmitt circuit 15 is operated at a voltage slightly lower than the voltage corresponding to device noise, and the second Schmitt circuit 22 is operated at a voltage slightly lower than the voltage corresponding to bulk erase noise or other tape running noise.

Therefore, the first Schmitt circuit 15 used in the tape end detection circuit 6 is configured to be operated at a higher voltage than the second Schmitt circuit 22. The third reference voltage circuit 18 and the second comparison circuit 19 shown in FIG.
and the first comparison circuit 17 is the first Schmitt circuit 15
This is a circuit that corresponds to However, tape signal detection circuit 5
Since the magnitude of the output signal of the first reference voltage circuit 16 and the first reference voltage circuit in the embodiment of FIG. When trying to substitute the comparison circuit 17 for the first Schmitt circuit 15 and the third reference voltage circuit 18 and the second comparison circuit 19 for the second Schmitt circuit 22, the first Schmitt circuit 15 is It has been partially changed so that it operates with an input signal (output signal of the tape signal detection circuit 5) lower than the set voltage set based on the output signal of the tape signal detection circuit 5 generated by the magnetic tape 1. Generates an output signal to switching circuit 14. The second Schmitt circuit is also partially modified to operate with an input signal lower than the set voltage (higher voltage than the first Schmitt circuit 15), and the integral time constant circuit 15 is operated between songs.
It is set to "generate an output signal in response to zero", and predetermined operations can be performed.

Conversely, the first Schmitt circuit 1 in the embodiment shown in FIG.
5 to the first reference voltage circuit 16 and the first comparison circuit 17
In addition, when the second Schmitt circuit 22 is substituted for the third reference voltage circuit 18 and the second comparator circuit 19, the first reference voltage circuit 16 is used to detect tape signals generated by device noise. The voltage is set slightly lower than the output signal of the circuit 5, and the first comparison circuit 17 is activated upon detecting that the output signal of the tape signal detection circuit 5 has become higher than the voltage of the first reference voltage circuit 16. , the end of the magnetic tape 1 is detected.

Further, the third reference voltage circuit 18 is set to a voltage slightly lower than the output signal of the tape signal detection circuit 5, which is generated due to noise other than signals such as device noise, bulk erase noise, etc. When it is detected that the output signal of the circuit 5 has become higher than the voltage of the third reference voltage circuit 18, the second comparison circuit 19 is activated, and a song interval can be detected.

As explained below, the circuit of the present invention is capable of detecting that at the end of the magnetic tape 1, the noise accompanying the running of the magnetic tape 1 disappears and only device noise remains.
Furthermore, it is possible to automatically detect the intervals between songs using a common circuit, which has the advantage of overcoming the drawbacks of the optical means mentioned at the beginning.

[Brief explanation of the drawing]

FIG. 1 shows an example of the noise spectrum of a magnetic recording/reproducing device. FIG. 2 shows one embodiment of the tape end detection circuit of the present invention, and FIG. 3 shows another embodiment of the tape end detection circuit of the present invention. 1... Magnetic tape 4... Magnetic reproducing head 5... Tape signal detection circuit 6.
...Tape end detection circuit 7 ... Song interval detection circuit 8 ... Amplifier circuit 9 ...
Filter circuit 10... Rectifier circuit 11...
... Smoothing circuit 12 ... Second reference voltage circuit 13 ... Division circuit 1
4... Switching circuit 15... First
Schmitt circuit 16...First reference voltage circuit 17...First comparison circuit 18...
...Third reference voltage circuit 19...Second comparison circuit 20...Integration time constant circuit 21...
・Switching circuit 22... Second Schmidt circuit patent applicant 弗 l Figure

Claims (1)

[Claims] (1) [A magnetic recording and reproducing device in which a magnetic tape is held between a capstan and a pinch roller and runs at a constant speed, comprising: A. a magnetic reproducing head that detects a signal from the magnetic tape; B. a tape signal detection circuit that amplifies and selects the output signal of the magnetic reproducing head; and C8 detects that the output signal of the tape signal detection circuit is greater than or equal to a first reference value or less than the first reference value. A tape end detection circuit comprising a tape end detection circuit and detecting the end of the magnetic tape based on the presence or absence of running noise of the magnetic tape; In a magnetic recording and reproducing apparatus that runs at a constant speed, A. a magnetic reproducing head that detects a signal of a magnetic tape; B. a tape signal detection circuit that amplifies and selects an output signal of the magnetic reproducing head; C1. D. A tape end detection circuit that detects that the output signal of the signal detection circuit is equal to or greater than a first reference value or less than the first reference value; and an inter-track detection circuit that detects whether the signal is above or below the second reference value, and detects that the output signal of the tape signal detection circuit is input to the tape end detection circuit and the inter-track detection circuit. Characteristic Tape End Detection Circuit (3) In the claims set forth in paragraphs (1) and (2), the tape signal detection circuit described above is
B. An amplifier circuit for amplifying the output signal of the magnetic head described above; B. A filter circuit for reducing the output level of a frequency band in which noise components are excessive among the output signals from the amplifier circuit and the magnetic head; C1. A tape end detection circuit (4) comprising: a rectifier circuit that rectifies the output signal amplified via the amplifier circuit; and D. a smoothing circuit that averages the output signal of the rectifier circuit. In the claims set forth in paragraphs 1) and (2), the tape end detection circuit described above comprises A,
B. The output voltage of the switching circuit that is non-conductive for an initial certain period of time during magnetic recording or magnetic reproducing operation, and the smoothing circuit described in paragraph (3) or the division circuit described in paragraph (4) is at the first reference value. or a Schmitt circuit that generates an output signal upon detecting that the voltage is below the first reference value (5) Clause (1) and ( In the claims set forth in item 2), the tape end detection circuit comprises: A, a switching circuit that is non-conductive for an initial fixed period of time during magnetic recording or magnetic reproducing operation, and B, a first reference voltage circuit. C0 for the output voltage of the first reference voltage circuit, the (3)
The invention is comprised of a comparator circuit that compares the output voltages of the rectifier circuits described in Section 1 and generates an output signal when it detects that the output voltage of the reference voltage circuit is higher than the output voltage of the rectifier circuit. Characteristic Tape End Detection Circuit (6) In the claims set forth in paragraphs (1) and (2), the above-described tape signal detection circuit comprises A. an amplifier that amplifies the output signal of the above-described magnetic head; B. A filter circuit for reducing the output level of a frequency band in which noise components are excessive among the output signals from the amplifier circuit and the above-mentioned magnetic head; C0. D. A smoothing circuit that averages the output signal of the rectifying circuit; E. A second reference voltage circuit; F. The output voltage of the second reference voltage circuit and the smoothing circuit that averages the output signal of the rectifying circuit; a division circuit that inputs each output voltage and performs a division calculation so that the output voltage of the reference voltage circuit is the numerator;
A tape end detection circuit comprising: