APPARATUS FOR MAGNETICALLY DETERMINING THE STATUS OF A CARTRIDGE IN A MAGNETIC RECORDER

Abstract: A magnet (20) is attached to a slidable tab (12) located on a magnetic tape cartridge (10). The slidable tab is movable between a write-protect position (16) for inhibiting recording on the tape in the cartridge, and a write-enable position (18). An associated recorder has two side-by-side Hall effect sensors (24, 26). When the cartridge is positioned in the recorder, the magnet, depending upon the selected position of the cartridge tab, is directly opposite to, and activates, only one or the other Hall effect sensor. If a first sensor is activated, then a write project circuit of the recorder is energized. If the second sensor is activated, then writing on the tape is permitted. If no cartridge is in the recorder, neither Hall effect sensor is activated, indicating that no cartridge is in place. The cartridge together with the recorder thereby provides write protection as well as a positive indication of the presence of the cartridge in the recorder.

Description: -1- APPARATUS FOR MAGNETICALLY DETERMINING THE STATUS OF A CARTRIDGE IN A MAGNETIC RECORDER Background Of The Invention 1. Technical Field Of The Invention This invention relates to a magnetic tape recorder and cartridge, and in particular, to determining certain relevant conditions of the cartridge when positioned in the recorder. 2. Description Relative To The Background Art It is known in the art that if a magnetic medium containing recorded information is later overwritten, the earlier stored information will be destroyed. If this occurs inadvertently, the result may be a complete loss of valuable data. For that reason, techniques have been developed to prevent unwanted erasure of the medium, and such techniques are known as "write protect" features. In a reel-to-reel recorder, write protect is generally accomplished by removal of a plastic ring ^ that is concentric with the reel hub. The absence of the ring is mechanically detected when the reel is mounted on the transport, and the write circuits accordingly are deactivated. Similarly in an audio cassette or data cartridge the presence or absence of either a plastic knockout or the position of a slidable tab allows a mechanical finger in the recorder to detect a write protect condition. Write protection exists when the finger motion is unimpeded as it enters the resulting void in the tape cassette or cartridge when the cassette or cartridge is inserted into the recorder. A floppy disk has a notch in the disk envelope which, when uncovered, plays a similar write protect role. Considered from the point of view of indications to the recorder itself, it will be noted that the write protect of the prior art functions to prevent recording when either there is no magnetic medium positioned in the recorder, or when the magnetic medium container has been set by the user to inhibit recording. In the prior art, write protect provides no specific indication that the magnetic medium is, in fact, in place in the recorder. DISCLOSURE OF INVENTION In view of the foregoing, an object of the invention is not only to provide a write protect capability in a cartridge-loaded recorder, but also to indicate positively that the cartridge is in its operating position. If there is no cartridge in the recorder, then it is not only desirable to inhibit the write function, but it is also necessary to completely inactivate the recorder tape drive system. This object is achieved by providing signals which can achieve this dual capability. In the practice of the invention, a small magnet is attached to a slidable tab located on the leading edge of the cartridge. Before insertion of the cartridge into the recorder, the slidable tab is moved by the user to one of two positions. One position is the write protect position for inhibiting recording on the tape in the cartridge, and the other position permits recording on the tape. The associated recorder has two side by side Hall effect sensors. When the cartridge is positioned in the recorder, the magnet, depending upon the selected position of the cartridge tab, is directly opposite to, and activates, only one or the other Hall effect sensors. The magnet's field strength and the location of the sensors are such that both sensors are never simultaneously activated; also, the field of the magnet cannot affect information recorded on the tape. If the cartridge is in the recorder, and if the first sensor is activated, then the write protect circuit of the recorder is energized. If the second sensor is activated, then writing on the tape is permitted. If no cartridge is in the recorder, neither Hall effect sensor is activated, indicating that no cartridge is in place. The invention thereby provides write protection as well as a positive indication of the presence of the cartridge in the recorder. BRIEF DESCRIPTION OF DRAWINGS The invention will be described with respect to the figures, of which: Fig. 1 is a perspective drawing of a magnetic tape cartridge and recorder in accordance with the invention, and Fig. 2 is a schematic circuit illustrating the operation of the invention. BEST MODE FOR CARRYING OUT THE INVENTION In the specification, the term "recorder" is used generically to signify either a magnetic recorder, a magnetic reproducer or a magnetic recorder and/or reproducer. Referring to Fig. 1, a cartridge 10 has a slidable tab 12 mounted on the cartridge 10 front face 13. The slidable tab 12, which is moveable in the direction of the doub-fce headed arrow 14, may be placed by the user into either the position 16 or the position 18. Mounted on the tab 12 is a magnet 20. When the cartridge 10 is mated with an associated recorder 22, and the slidable tab 12 is in the position shown, the magnet 20 is adjacent to a Hall effect sensor 24 located in the recorder 22. When the slidable tab 12 is in the position 18, the magnet 20 is adjacent to a second Hall effect sensor 26. The position ' 16 adjacent to -4- the sensor 24 may be designated the "write protect" position, and the position 18 adjacent to the sensor 26 may be designated as the "non write protect" position. 5 Referring to Fig. 2, the slidable tab 12 is shown in position 16 where the magnetic field lines 21 of the magnet 20 are intercepted by the Hall effect sensor 24. Under these conditions the Hall effect sensor 24 conducts causing current to flow in 10 the resistor 28 which sets the input terminal of the inverting buffer amplifier 30 at ground potential. The output of the amplifier 30 rises, resulting in a positive going signal "A" which is the Write Protect signal. This Write Protect signal serves to activate 15 circuitry (not shown) that prevents a write operation from occurring. If the slidable tab 12 is in the position 18, the magnet 20 now causes the Hall effect sensor 26 to conduct current, and the output of the 20 inverting buffer amplifier 34 rises resulting in positive going signal "B" which is the "Non-Write Protect" signal. This Non-Write Protect signal serves to activate circuitry (not shown) that enables a write operation to occur. 25 The magnet's field strength and the location of the sensors are such that both sensors are never simultaneously activated; also, the field of the magnet cannot affect information recorded on the tape. That is, the coercivity of the magnet is no 30 greater than the coercivity of the tape. The "A" and "B" signals feed an "Or" circuit 36, which in turn feeds the input of an inverting buffer amplifier 38. If either the "A" or "B" signal are high, the output of the "Or" circuit 36 is high, 35 and the output of the amplifier 38 is low, i.e. "C" is low, which signals that there is a cartridge in the recorder. If both the "A" and "B" signals are low, the output of the amplifier 38 is high, i.e. "C" is high, which signals there is no cartridge inserted in the recorder. Additionally, if the cartridge containing a tape having a pre-recorded servo track is inadvertently subjected to erasure of the servo track by exposure, for example, to a degaussing field, the magnet on the tab may be so selected that it will also be erased. Then upon insertion of the cartridge into the recorder, neither Hall effect sensor will be activated; that is, it will appear to the recorder that no cartridge is in place, and the tape drive system will not be energized. On the other hand, in a recorder application where a cartridge is to be intentionally erased by degaussing, the magnet may be selected with a high enough coercivity to make it immune from demagnetization by a typical degausser. Fixed magnets may also be located on the cartridge for activating other Hall effect sensors in the recorder. These magnets may be configured to indicate a classification of the cartridge to specify the recorder with which it is compatible, or to specify the type of tape loaded in the cartridge. The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. For example, provision may be made for mounting one or two fixed magnets at the opposite end of the same edge of the cartridge, and for mounting two additional Hall effect sensors in the recorder positioned opposite to the additional magnets of the inserted cartridge. Such a configuration exhibits four possible states, depending on the number of additional magnets in place and their positions. In this manner the cartridge may be classified for use is one or more of a family of recorders, or the magnetic configuration may be used to identify the type of tape in the cartridge.

Claims: What Is Claimed Is: 1. The combination of a magnetic tape cartridge (10) and recorder apparatus (22) adapted to receive said cartridge, said cartridge characterized by: a) an actuatable member 12 movably mounted on said cartridge for movement between (1) a first write enabled position, and (2) a second write-protect position; and b) a magnet (20) carried by said actuatable member; said recorder apparatus characterized by c) magnetic-field sensing means (24, 26) located in said recorder apparatus (1) to sense the magnetic field of said magnet when said cartridge is loaded into said recorder apparatus, and (2) to distinguish, in response to the magnetic field sensed, whether said actuatable member is in its write enabled position or in its write-protect position; and d) control circuitry (30, 34, 36, 38), responsive to said sensing means, for producing a control signal indicating the presence or absence of said cartridge in said recorder apparatus. 2. The combination of Claim 1 wherein the coercivity of said magnet is no greater than the coercivity of the magnetic tape in said cartridge.

Inventors: KARSH HERBERT, KARSH, HERBERT
Applicants: EASTMAN KODAK CO, EASTMAN KODAK COMPANY
Application year: 1990
Main classification: G11B23
IPC codes: G11B15, G11B23