GB1565222A - Detection of nonrecoreded section of a magnetic tape non-recorded section of magnetic tape - Google Patents

Detection of nonrecoreded section of a magnetic tape non-recorded section of magnetic tape Download PDF

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Publication number
GB1565222A
GB1565222A GB3537076A GB3537076A GB1565222A GB 1565222 A GB1565222 A GB 1565222A GB 3537076 A GB3537076 A GB 3537076A GB 3537076 A GB3537076 A GB 3537076A GB 1565222 A GB1565222 A GB 1565222A
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United Kingdom
Prior art keywords
capacitor
amplifier
power supply
transistor
recorded
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB3537076A
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Sharp Corp
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Sharp Corp
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Publication date
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Publication of GB1565222A publication Critical patent/GB1565222A/en
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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B15/00—Driving, starting or stopping record carriers of filamentary or web form; Driving both such record carriers and heads; Guiding such record carriers or containers therefor; Control thereof; Control of operating function
    • G11B15/02—Control of operating function, e.g. switching from recording to reproducing
    • G11B15/10—Manually-operated control; Solenoid-operated control
    • G11B15/103—Manually-operated control; Solenoid-operated control electrically operated
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
    • G11B27/19—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier
    • G11B27/22—Means responsive to presence or absence of recorded information signals
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
    • G11B27/36—Monitoring, i.e. supervising the progress of recording or reproducing

Description

(54) DETECTION OF NONRECORDED SECTION OF A MAGNETIC TAPE (71) We, SHARP KABUSHIKI KAISHA, a Japanese company of, 22-22 Nagaike-cho, Abeno-ku, Osaka, 545, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a magnetic tape-record apparatus including a non-recorded section detecting system.
In a conventional non-recorded section detection system, when a tape feed mechanism is in a fast drive mode, a charge/discharge circuit is connected to receive an output signal of an amplifier associated with a reproduction head so that charging takes place when the reproduction head contacts a recorded section of tape.
When the charge level of the charge-discharge circuit falls below a predetermined value after the reproduction head reaches a non-recorded section, the tape feed mechanism is automatically shifted to a normal playback mode.
It is important in the above-mentioned non-recorded section detection system of the prior art for the output level of the amplifier to be high to ensure accurate operation. Moreover, variations of the power supply voltage greatly influence the accuracy of the detection of the nonrecorded section in the prior art system.
In accordance with the invention there is provided magnetic-tape-record apparatus comprising a tape feed mechanism, control means for controlling said mechanism, a magnetic tape reproduction head for sensing magnetically recorded information on a magnetic tape, an amplifier for amplifying an output from said reproduction head, and a system for detecting a non-recorded section between adjacent recorded sections of the magnetic tape, the system comprising: solid state switching means responsive during a fast drive mode of said feed mechanism to an output signal of the amplifier and arranged to adopt a first state when the output signal is above a predetermined level and a second state when the output signal is below the predetermined level; a charge/discharge circuit arranged to receive a charge current from a power supply source through said solid state switching means when solid state switching means is in one of said states; and a solid state electronic level detector arranged to provide an output dependent upon whether the charge level of said charge/discharge circuit is greater or less than a threshold level, and indicative of whether a nonrecorded section has been detected, said control means being responsive to the level detector output to change the mode of said feed mechanism.
Arrangements embodying the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a circuit diagram of a nonrecorded section detection system in a taperecord apparatus of the prior art; Figure 2 is a circuit diagram of an embodiment of a non-recorded section detection system of the present invention; Figure 3 is a circuit diagram of another embodiment of a non-recorded section detection system of the present invention; and Figure 4 is a schematic circuit diagram of a magnetic-tape-record apparatus employing a non-recorded section detection system of the present invention.
Referring now in detail to the drawings, and to facilitate a more complete understanding of the present invention, a non-recorded section detection system of the prior art will be first described with reference to Figure 1.
A non-recorded section detection switch 3 is mechanically associated with a tape feed mechanism. When the non-recorded section detection switch 3 is closed, the tape feed mechanism is shifted to a fast feed mode and the system is placed in a non-recorded section detection mode, whereby a limiter/amplifier 2 is connected to a power supply through the non-recorded section detection switch 3. Under these conditions, when a magnetic tape reproduction head 1 contacts a recorded section of the magnetic tape. the limiter/amplifier 2 develops an output signal to charge a charge/discharge circuit i through a capacitor 4 and a rectifying circuit 5.
When the reproduction head 1 reaches a non-recorded section, the limiter/amplifier 2 ceases to develop the charging signal and, therefore, the charge stored in a capacitor 8 is discharged through a resistor 9. When the charged level across the capacitor 8 falls below a predetermined value, a level detector 10 in the form of a Schmitt trigger circuit is actuated, and this causes the tape feed mechanism to be shifted into the normal playback mode from the fast feed mode.
The time delay in the circuit 7, that is, the time interval beginning at the termination of the output signal from the limiter/amplifier 2 and ending at the switching of the level detector 10 is a very important factor in performing an accurate operation. This time interval varies greatly when the power supply voltage +B varies in the prior art system, because the charge/discharge circuit 7 receives the output signal of the limiter/amplifier 2 as its charging current and the output level of the limiter/amplifier 2 changes considerably with variations in the power supply level +B.
Figure 2 shows an embodiment of a nonrecorded section detection system of the present invention, which comprises a magnetic tape reproduction head 1, a limiter/amplifier 2, a non-recorded section detection switch 3 associated with the tape feed mechanism, a capacitor 4, a resistor 31, and a switching transistor 6, the capacitor 4, the resistor 31 and the switching transistor 6 forming, in combination, a switching means for controlling delivery of a charge current.
The present non-recorded section detection system further comprises a charge/discharge circuit 7 including a capacitor 8 and a resistor 9, a level detector 10 in the form of a Schmitt trigger circuit including transistors Il and 12, a differentiation circuit 13 including a capacitor 14 and a resistor 15, a transistor 16, and a protective diode 17 for the transistor 16.
When the non-recorded section detection switch 3 is closed during the playback mode, the tape feed mechanism is shifted to a fast feed mode and the system is placed in the non-recorded section detection mode. The reproduction signal from the reproduction head I is applied to the limiter/amplifier 2, which develops an output signal to the base electrode of the switching transistor 6 through a coupling circuit formed by the capacitor 4 and the resistor 31. When the output level of the limiter/amplifier 2 is above the base to emitter voltage VBE of the switching transistor 6, the switching transistor 16 is ON and, hence, the capacitor 8 is charged up to the power supply voltage +B by current passing through the transistor 6. The charged voltage is applied to the level detector 10, whereby the transistor 11 is ON and the transistor 12 is OFF. The collector electrode () of the transistor 12 is main tained at the power supply level +B. The transistor 16 is OFF and, hence, a solenoid 18 is noenabled, because no voltage differ ence appears across the capacitor 14.
When the reproduction head 1 reaches a non-recorded section, the limiter/amplifier 2 ceases to develop its output signal and, therefore, the switching transistor 6 is turned OFF. The voltage across the capacitor 8 is discharged through the resistor 9. The transistor 11 is turned OFF and the transistor 12 is turned ON after a time period determined by the time constant of the charge/discharge circuit 7 and the threshold level of the level detector 10. At this moment the collector electrode Qj) of the transistor 12 is maintained at about the ground potential and, therefore, a charge current for the capacitor 14 flows .through the power supply +B, the resistor 15, the capacitor 14 and the point. This current renders the transistor 16 ON and, hence, the solenoid 18 is enabled. The solenoid 18 functions to shift the tape feed mechanism back into its normal playback mode and to reset the non-recorded section detection switch 3.
In the foregoing embodiment, the charge/discharge circuit 7 is connected to the power source voltage +B through the switching transistor 6 when the reproduction signal is derived from the limiter/amplifier 2. Therefore, the output level of the limiter/amplifier 2 does not need to be as high as in the prior art, but merely sufficient to turn on the switching transistor 6. Moreover, the variations of the power supply voltage +B are self-compensated.
When the power supply voltage +B rises, both the voltage to which the capacitor 8 is charged and the threshold level of the level detector 10 are increased.
The differentiation circuit 13 functions to prevent erroneous operation of the transistor 16. More particularly, the differentiation circuit 13 detects the trailing edge of the signal appearing at the point , thereby turning on the transistor 16 only when the non-recorded section is detected after the provision of the reproduction signal.
Figure 3 shows another embodiment of the non-recorded section detection system of the present invention. Like elements corresponding to those of Figure 2 are indicated by like numerals.
In the embodiment of Figure 2, there is a possibility that a charging current will flow to the capacitor 14 and the capacitor 4 when the apparatus is switched on. The charging current flowing to the capacitor 14 will turn on the transistor 16 and, hence, the solenoid 18 is enabled. The charging current flowing to the capacitor 4 will turn on the transistor 6, thereby charging the capacitor 8.
Therefore, the solenoid 18 will be enabled after a time period determined by the time constant of the charge/discharge circuit 7 and the threshold level of the level detector 10.
An erroneous operation preventing circuit 20 functions to prevent the abovementioned erroneous operation when the apparatus is switched on. When a power switch 19 is closed, a charging current flows to the capacitor 4 through the power supply source +B, the resistor 31, the capacitor 4 and the limiter/amplifier 2. At this moment a switching transistor 23 functions to disconnect the transistor 6 from the capacitor 4. A charging current also flows to the capacitor 14 through the power supply source +B, the resistor 15, the capacitor 14 and the level detector 10 when the power switch 19 is closed. At this moment a switching transistor 24 functions to disconnect the transistor 16 from the capacitor 14.
The base electrodes of the switching transistors 23 and 24 are connected to each other and to a delay circuit comprising a resistor 21 and a capacitor 22. When the power switch 19 is closed, a charging current flows to the capacitor 22 through the power supply source +B, the resistor 21 and the capacitor 22, whereby the voltage level appearing across the capacitor 22 is increased from zero toward the power supply voltage +B. The switching transistors 23 and 24 are maintained OFF until the voltage level appearing across the capacitor 22 becomes higher than the emitter levels of the transistors 23 and 24 by the base to emitter voltage +VBE. During the time period when the transistors 23 and 24 are OFF, the resistor 31, the capacitor 4, the transistor 6, the differentiation circuit 13 and the transistor 16 are disconnected. The aforementioned erroneous operation of the solenoid 18 at the time the apparatus is switched on can be prevented by selecting the time period when the transistor 23 and 24 are OFF longer than the time required to charge the capacitors 4 and 14.
Figure 4 shows an example of a magnetictape-record apparatus employing the nonrecorded section detection system of the present invention. An output signal of an equalization amplifier 25 is applied to an audio-frequency amplifier 29 via an elect tronic attenuator 26. The output signal of the amplifier 29 activates a speaker 30. The output signal of the equalization amplifier 25 is also applied to the limiter/amplifier 2 associated with the non-recorded section detection system. In the non-recorded section detection mode, the output level of the reproduction head 1 is greater than that of the normal playback mode, because the tape feed speed is considerably faster.
Therefore, the monitor sound derived from the speaker 30 is very loud. In the taperecord apparatus of the prior art, the audiofrequency amplifier 29 is cut-off, thereby preventing the activation of the speaker 30 during the non-recorded section detection operation.
In the example of Figure 4, a lowamplitude monitor sound is derived from the speaker 30, thereby indicating the nonrecorded section detection mode. The electronic attenuator 26 includes a resistor 27 and an electronic variable resistor element 28 formed by for example, a transistor 28-a or a diode 28-b.
The input level of the resistor element 28 is zero when the non-recorded section detection switch 3 is open and, therefore, the output impedance of the element 28 is very high. The output signal of the equalization amplifier 25 is applied to the audio-frequency amplifier 29 without attenuation.
The input terminal of the element 28 is connected to the power supply source +B when the non-recorded section detection switch 3 is closed and the system is placed in the non-recorded section detection mode.
The output impedance of the element 28 is reduced and, therefore, the output signal of the equalization amplifier 25 is applied to the audio-frequency amplifier 29 after being attenuated by the resistor 27 and the output impedance of the element 28.
The apparatus described above is also described, and certain aspects thereof claimed, in our copending Patent Application No. 14983/79 which was divided from the present application. Reference is also directed to our earlier U.K. Patent No.
1,448,738, which relates to magnetic-taperecord players having a control arranged to discontinue a fast drive mode only when a non-recorded section of tape is detected after a recorded section has first been detected.
WHAT WE CLAIM IS: 1. Magnetic-tape-record apparatus comprising a tape feed mechanism, control means for controlling said mechanism, a magnetic tape reproduction head for sensing magnetically recorded information
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. corresponding to those of Figure 2 are indicated by like numerals. In the embodiment of Figure 2, there is a possibility that a charging current will flow to the capacitor 14 and the capacitor 4 when the apparatus is switched on. The charging current flowing to the capacitor 14 will turn on the transistor 16 and, hence, the solenoid 18 is enabled. The charging current flowing to the capacitor 4 will turn on the transistor 6, thereby charging the capacitor 8. Therefore, the solenoid 18 will be enabled after a time period determined by the time constant of the charge/discharge circuit 7 and the threshold level of the level detector 10. An erroneous operation preventing circuit 20 functions to prevent the abovementioned erroneous operation when the apparatus is switched on. When a power switch 19 is closed, a charging current flows to the capacitor 4 through the power supply source +B, the resistor 31, the capacitor 4 and the limiter/amplifier 2. At this moment a switching transistor 23 functions to disconnect the transistor 6 from the capacitor 4. A charging current also flows to the capacitor 14 through the power supply source +B, the resistor 15, the capacitor 14 and the level detector 10 when the power switch 19 is closed. At this moment a switching transistor 24 functions to disconnect the transistor 16 from the capacitor 14. The base electrodes of the switching transistors 23 and 24 are connected to each other and to a delay circuit comprising a resistor 21 and a capacitor 22. When the power switch 19 is closed, a charging current flows to the capacitor 22 through the power supply source +B, the resistor 21 and the capacitor 22, whereby the voltage level appearing across the capacitor 22 is increased from zero toward the power supply voltage +B. The switching transistors 23 and 24 are maintained OFF until the voltage level appearing across the capacitor 22 becomes higher than the emitter levels of the transistors 23 and 24 by the base to emitter voltage +VBE. During the time period when the transistors 23 and 24 are OFF, the resistor 31, the capacitor 4, the transistor 6, the differentiation circuit 13 and the transistor 16 are disconnected. The aforementioned erroneous operation of the solenoid 18 at the time the apparatus is switched on can be prevented by selecting the time period when the transistor 23 and 24 are OFF longer than the time required to charge the capacitors 4 and 14. Figure 4 shows an example of a magnetictape-record apparatus employing the nonrecorded section detection system of the present invention. An output signal of an equalization amplifier 25 is applied to an audio-frequency amplifier 29 via an elect tronic attenuator 26. The output signal of the amplifier 29 activates a speaker 30. The output signal of the equalization amplifier 25 is also applied to the limiter/amplifier 2 associated with the non-recorded section detection system. In the non-recorded section detection mode, the output level of the reproduction head 1 is greater than that of the normal playback mode, because the tape feed speed is considerably faster. Therefore, the monitor sound derived from the speaker 30 is very loud. In the taperecord apparatus of the prior art, the audiofrequency amplifier 29 is cut-off, thereby preventing the activation of the speaker 30 during the non-recorded section detection operation. In the example of Figure 4, a lowamplitude monitor sound is derived from the speaker 30, thereby indicating the nonrecorded section detection mode. The electronic attenuator 26 includes a resistor 27 and an electronic variable resistor element 28 formed by for example, a transistor 28-a or a diode 28-b. The input level of the resistor element 28 is zero when the non-recorded section detection switch 3 is open and, therefore, the output impedance of the element 28 is very high. The output signal of the equalization amplifier 25 is applied to the audio-frequency amplifier 29 without attenuation. The input terminal of the element 28 is connected to the power supply source +B when the non-recorded section detection switch 3 is closed and the system is placed in the non-recorded section detection mode. The output impedance of the element 28 is reduced and, therefore, the output signal of the equalization amplifier 25 is applied to the audio-frequency amplifier 29 after being attenuated by the resistor 27 and the output impedance of the element 28. The apparatus described above is also described, and certain aspects thereof claimed, in our copending Patent Application No. 14983/79 which was divided from the present application. Reference is also directed to our earlier U.K. Patent No. 1,448,738, which relates to magnetic-taperecord players having a control arranged to discontinue a fast drive mode only when a non-recorded section of tape is detected after a recorded section has first been detected. WHAT WE CLAIM IS:
1. Magnetic-tape-record apparatus comprising a tape feed mechanism, control means for controlling said mechanism, a magnetic tape reproduction head for sensing magnetically recorded information
on a magnetic tape, an amplifier for amplifying an output from said reproduction head, and a system for detecting a non-recorded section between adiacent recorded sections of the magnetic tape, the system comprising: solid state switching means responsive during a fast drive mode of said feed mechanism to an output signal of the amplifier and arranged to adopt a first state when the output signal is above a predetermined level and a second state when the output signal is below the predetermined level; a charge/discharge circuit arranged to receive a charge current from a power supply source through said solid state switching means when said solid state switching means is in one of said states; and a solid state electronic level detector arranged to provide an output dependent upon whether the charge level of said charge/discharge circuit is greater or less than a threshold level, and indicative of whether a non-recorded section has been detected, said control means being responsive to the level detector output to change the mode of said feed mechanism.
2. Apparatus as claimed in claim 1, wherein the level detector is arranged such that the threshold level changes in accordance with variations in the level of said power supply source to provide compensation for changes in the voltage to which said charge/discharge circuit is charged due to said variations.
3. Apparatus as claimed in claim 1 or 2, wherein the level detector comprises a Schmitt trigger circuit.
4. Apparatus as claimed in any preceding claim, wherein said switching means comprises a transistor the base of which is arranged for receiving the output signal of said amplifier, and having a main current-carrying electrode connected to said charge/discharge circuit.
5. Apparatus as claimed in any preceding claim, including means for preventing said switching means from operating said charge/discharge circuit when the system is initially connected to said power supply source.
6. Apparatus as claimed in claim 5, wherein said preventing means comprises a semi-conductor switch which is in use coupled between said amplifier and said switching means, said semi-conductor switch being off when said system is initially connected to said power supply source thereby to prevent the operation of said switching means, the preventing means also including delay means for turning said semiconductor switch on at a predetermined time after said initial connection of said system to said power supply source.
7. Apparatus as claimed in any preceding claim, further comprising means for differentiating the output of said level detector to provide a differentiated output signal when a non-recorded section is detected after a recorded section has first been detected.
8. Apparatus as claimed in claim 7, further comprising means for preventing said differentiated output from being applied to said control means when said system is initially connected to said power supply source.
9. Apparatus as claimed in claim 8, wherein said preventing means comprises a semi-conductor switch coupled between said differentiation means and said control means, and arranged to be off when said system is initially connected to said power supply source, the preventing means further including time delay means for turning said semi-conductor ' switch on at a predetermined time after said initial connection of said system so said power supply source.
10. Apparatus as claimed in any preceding claim, further comprising a nonrecorded section detection switch for placing said system into an operative condition.
11. Apparatus as claimed in claim 10, wherein said non-recorded section detection switch is mechanically coupled to said tape feed mechanism.
12. Apparatus as claimed in any preceding claim, wherein the control means comprises a solenoid operable to shift the operation mode of said tape feed mechanism.
13. Apparatus as claimed in any preceding claim, wherein the amplifier is a limiter/amplifier.
14. Magnetic-tape-record apparatus including a system for detecting a nonrecorded section between adjacent recorded sections of a magnetic tape, the system being substantially as herein described with reference to Figure 2 or Figure 3 of the accompanying drawings.
15. Magnetic-tape-record apparatus substantially as hereinbefore described with reference to Figures 2 and 4, or Figures 3 and 4, of the accompanying drawings.
GB3537076A 1975-08-28 1976-08-25 Detection of nonrecoreded section of a magnetic tape non-recorded section of magnetic tape Expired GB1565222A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP17397675 1975-08-28

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GB1498379A Expired GB1565223A (en) 1975-08-28 1976-08-25 Detection of nonrecorded section of a magnetic tape
GB3537076A Expired GB1565222A (en) 1975-08-28 1976-08-25 Detection of nonrecoreded section of a magnetic tape non-recorded section of magnetic tape

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GB1498379A Expired GB1565223A (en) 1975-08-28 1976-08-25 Detection of nonrecorded section of a magnetic tape

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2242302A (en) * 1990-03-21 1991-09-25 Samsung Electronics Co Ltd Automatic search apparatus and method for a record/play or play system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2242302A (en) * 1990-03-21 1991-09-25 Samsung Electronics Co Ltd Automatic search apparatus and method for a record/play or play system
GB2242302B (en) * 1990-03-21 1994-05-25 Samsung Electronics Co Ltd Automatic search apparatus and method for a record/play or play system

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PS Patent sealed
PE20 Patent expired after termination of 20 years

Effective date: 19960824