Abstract: A lens system is provided. The lens system includes a first lens system moveable between a first position removed from an optical axis and a second position on the optical axis. The first lens system includes a first lens element, an aperture stop, and a second lens element positioned in order from an object side to an image side of the lens system. The first lens system has a first focal length. A second lens system is moveable between a first position on the optical axis and a second position removed from the optical axis. The second lens system has a second focal length with the second focal length being greater than the first focal length such that a magnification ratio change results from interchanging the first lens system and the second system on the optical axis.

Abstract: An image-capturing lens includes a plastic lens formed with use of a material in which particles each having the maximum length of 30 nanometer or less are dispersed in a plastic material.

Abstract: The present invention provides a miniature zoom lens having a first, a second, a third, a fourth, and a fifth lens group from object side to image side in order. The powers of those lens groups in same order are positive, negative, positive, positive, and positive. The first lens group for receiving light and the third lens group are fixedly positioned. The second lens group for zooming, the fourth lens group for compensating aberration and the fifth lens group for focusing are movably positioned. When the zoom lens is zoomed from wide status to telephoto status, the second lens group is moved toward the third lens group, the fourth lens group is moved close to the third lens group. The sensitivity of the zoom lens is determined by second lens group to simplify the adjusting and proofing procedures of other lens groups.

Abstract: An imaging-optical system includes a negative first lens group, a positive second lens group and a positive third lens group. A zooming operation is performed by moving the second and third lens groups while an object distance to the object is being varied without varying a distance from the most object-side surface of the first lens group to the imaging plane. An in-focus state is maintained while the focal length of the imaging-optical system is being varied through the zooming operation. The first lens group includes cemented lens elements, and the cemented lens elements are positioned at the most object-side of the first lens group. The cemented lens elements satisfy the following condition: 0.9<Ra/fw<2.0??(1) wherein Ra designates the radius of curvature of a bonding surface of the cemented lens elements of the first lens group; and fw designates the focal length of the imaging-optical system at the short focal length extremity.

Abstract: Object is to provide an inner-focusing type zoom lens system carrying out focusing by moving a portion of a first lens group suitable for an auto-focus SLR camera. A zoom lens system includes, in order from an object, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. Upon zooming from a wide-angle end state to a telephoto end state, a distance between the first and the second lens groups increases, and a distance between the second and the third lens groups decreases. The first lens group is composed of, in order from the object, a 1A lens group G1A having positive refractive power, and a 1B lens group G1B having positive refractive power. Focusing from infinity to a close-range object is carried out by moving only the 1B lens group G1B to the object.

Abstract: A suspension apparatus comprises a lens holder, a suspension spring and a supporting base. The supporting base is formed with an opening for accommodating the lens holder. The lens holder is for positioning a lens unit. The suspension spring is manufactured by stamping process to form a long strip with a plurality of suspension springs. The strip is then guided into a mold, and plastic injection molding process is performed in that mold so as to produce the lens holder and supporting base affixed respectively to either end of the suspension spring in one piece. After that, excess material of the strip is cut off. The suspension apparatus as above described is suitable for mass production. In addition, because of the high precision of mold, the inaccuracy of assembly and fabrication is minimized. The volume of the whole apparatus and the cost of production are also vastly decreased.

Abstract: The instant invention is an optical imaging system that produces images of acceptable quality of objects which are located at a wide variety of distances from the optical imaging system. A preferred embodiment of the optical imaging system includes an object (10), an auxiliary lens (12), a composite phase marsk (14) and a detector (18) arranged along an optical axis (20). Light from the object (10) is focused by the auxiliary lens (12) in tandem with the composite phase mark (14), producing an image (16) which is incident th detector (18).

Abstract: A ring-shaped flare stopper is made of a phosphor bronze plate having a thickness of 0.03 mm by sheet metal stamping. An inner periphery for defining a circular opening is formed in the flare stopper. The inner periphery has the form of the side face of a circular truncated cone. The flare stopper is so installed in a lens barrel that the inner periphery is inclined with respect to an optical axis of a taking lens unit. Since incident light is not reflected by the inner periphery of the flare stopper, the occurrence of ghost and flare is prevented. To prevent the deformation and misalignment of the flare stopper, the flare stopper installed in the lens barrel is attached to a spacer.

Abstract: It is to provide an imaging lens system which, while reduced in size and weight, can fully meet the demand for more improvement in the optical performance and also improvement in the productivity. The imaging lens system comprises, in order from an object side towards an image surface side, a diaphragm, a first lens which is a meniscus lens having a positive power whose concave surface facing the object side, and a second lens which is a meniscus lens having a negative power whose convex surface facing the image surface side, wherein the Abbe number of the second lens is set smaller than the Abbe number of the first lens.

Abstract: Disclosed is an optical system in which an adhesive layer of a cemented lens is made of a mixture in which inorganic fine particles dispersed into a transparent medium. Therefore, there is realized an optical system capable of effectively correcting chromatic aberration while having a structure in which a manufacturing cost is low and an environmental resistance is high.

Abstract: A pre-scan assembly for a laser scanning unit including printhead housing having a polygonal mirror and collimation assembly including a laser light source emitting a light beam along a light beam axis. The pre-scan assembly is located between the collimation assembly and the polygonal mirror and includes a pre-scan lens assembly including a carrier and a pre-scan lens supported in the carrier. The pre-scan assembly additionally includes a pre-scan mount for supporting the pre-scan lens assembly and defining angular alignment surfaces. The carrier includes outer side surfaces for engaging the angular alignment surfaces where engagement of the carrier side surfaces with the angular alignment surfaces aligns the pre-scan lens optical axis with the light beam axis in the scan direction.

Abstract: To provide a lens device involving simple adjustment work and an adjustment method for the same, the lens device includes the first and second lens groups, each including having a retaining guide section on a surface facing another of the first and second lens groups, wherein the retaining guide section of one of the first and second lens groups retains and guides the other of the first and second lens groups so that the other of the first and second lens groups can rotate around the optical axis in the rotary cylinder.

Abstract: Disclosed is an optical filter switching apparatus used in an optical instrument for converting externally input image information into video image information and outputting the video image information. The apparatus comprises: an optical filter holding section holding a first optical filter and a second optical filter; an actuator having a rotary solenoid which rotates between a first position and a second position. A rotational power transmission section transmits the rotational force of the rotary solenoid to the optical filter holding section; and a microprocessor controls the rotary solenoid of the actuator in accordance with at least one external input signal and the power level of the video image information. The rotary solenoid is rotated to at least one of the first and second positions.

Abstract: A partial response maximum likelihood (PRML) data detecting in a magnetic recording storage device is carried out with a preliminary measuring of write-read channel responses to all nonzero binary combinations of a given length. Decoding of the user data is performed according to a Viterbi algorithm, where the previously measured responses are used as expected samples for branch metric calculations. The measurement of the write-read channel responses and the decoding of the user data are fulfilled by a self-adjusting PRML receiver that contains a controllable clock recovery, a responses accumulator and an adjustable Viterbi detector. The controllable clock recovery produces a set of read-back signal samples containing exactly one sample per bit with or without phase error correction. The responses accumulator calculates averaged responses of the write-read channel. The adjustable Viterbi detector reconstructs the user data that were written to the disk.

Abstract: A disk drive detects head touchdown based on a magnitude of a position error signal at a discrete frequency. The discrete frequency is one-half the disk rotation frequency or an integral multiple of the disk rotation frequency. The head is heated by turning on a heater at the discrete frequency, thereby injecting bias into a servo system that increases the PES magnitude. In addition, the servo system has a first transfer function for tracking the head during read and write operations and a second transfer function for tracking the head during head touchdown detection. The second transfer function has smaller vibration rejection than the first transfer function so that the disk drive is less sensitive to vibration during read and write operations than during head touchdown detection.

Abstract: A data storage library for storing a storage media, wherein a plurality of accessors accesses the data storage media stored in an array of storage cells includes a first accessor transporting the storage media, the first accessor including a first carriage storing or retrieving the storage media on to the storage cell and a first guide guiding the first carriage moving vertically; a second accessor transporting the storage media, the second accessor including a second carriage storing or retrieving the storage media on to the storage cell and a second guide guiding the second carriage moving vertically; and a third guide guiding the first accessor and the second accessor moving horizontally. The first carriage opposes the second carriage and the first and second carriages are in a staggered configuration, when the first guide exists between the array and the second guide.

Abstract: A storage apparatus comprises at least one housing A in which a storage device and a controller are provided, at least one housing B in which a storage device and a peripheral device are provided, and a transmission path for connecting the storage device and the controller of the housing A, and the storage device of the housing B to enable communication therebetween. The storage apparatus is capable of controlling operation of the storage device of the housing B according to an operating state of the storage device of the housing A through communication via the transmission path; and controlling operation of the peripheral device according to an operating state of the storage device of the housing B.

Abstract: A disc drive having a multi-phase acceleration procedure is disclosed. The multi-phase acceleration procedure accelerates a data storage disc in the disc drive from an initial rotational velocity to a final rotational velocity. As the disc reaches the final rotational velocity, a read/write head operable to access data on the disc is moved by a servo control system from a landing zone to a data region on the disc. An air bearing between a slider of the read/write head and the surface of the disc is created due to the final rotational velocity of the spinning disc. The read/write head may also be moved from the landing zone as the disc reaches an early exit rotational velocity. As such, the multi-phase acceleration procedure continues accelerating the disc until the final rotational velocity to guarantee that the air bearing is maintained between the head and the disc.

Abstract: A disk drive is disclosed comprising a disk, a head actuated over the disk, and a spindle motor for rotating the disk, the spindle motor comprising a plurality of windings. Disk control circuitry executes a spin-down operation of the spindle motor by estimating an angular position of the spindle motor by applying a voltage to at least one of the windings and evaluating a rise time of current flowing through the winding. The windings are commutated in response to the estimated angular position, and a driving current is applied to the windings to brake the spindle motor.

Abstract: What is disclosed is a method and apparatus for writing servo information on disks to be used in a hard disk drive assembly. In one embodiment, servo information is pre-written onto a disk using an offline servo track writer which employs a fluid dynamic bearing spindle to rotate the disk(s) during read/write operations. In another embodiment, servo information is written onto a disk by a method of track following on a reference disk using an offline servo track writer.

Abstract: A disk drive includes a casing which houses a disk-shaped recording medium, a drive motor which holds and rotates the recording medium, a head which performs read/write operations, a head actuator movably supporting the head to move the head relative to the recording medium, and a board unit connected to the head actuator. The board unit has a board main body arranged on the inner surface of the casing and at least one capacitor, mounted on the board main body for supplying power to perform a retracting operation for permitting the head actuator to move the head to a retracted position.

Abstract: The present invention provides a magnetic disk storage system including a spindle motor that rotates a magnetic disk, a spindle motor drive circuit that rotatably drives the spindle motor, a magnetic head that performs reading of information on the magnetic disk, a voice coil motor that moves the magnetic head, and a voice coil motor drive circuit that drives the voice coil motor. When the magnetic head is loaded from a standby position to the surface of the magnetic disk, the rotational speed of the spindle motor is made slower than a rotational speed at a normal operation. Upon power-off, the spindle motor drive circuit is caused to carry out a stepup converter operation to thereby generate a voltage higher than a back electromotive voltage, and causes a control circuit and a drive circuit to operate by the high voltage to thereby enable speed control at the movement of the magnetic head to a predetermined standby position.

Abstract: An apparatus, method, and system for providing a fine adjustment for transducing head positioning in a hard disk drive (HDD). The apparatus, method, and system include reading a positioning error field wherein the resulting signal is a substantially sinusoidal position error signal (PES), filtering the PES to remove low frequencies and attenuate high frequencies, sample the filtered PES at a multiple of the channel frequency, filter the higher frequency harmonics, down sample the PES, and provide a signal proportional to the amplitude of the down sampled PES. This signal is the reference signal to the head positioning servo.

Abstract: A head positioning control system which is applied to a disk drive is disclosed. The system includes a feedback control system which performs head positioning control of a head and a feedforward control system. The feedforward control system detects the amplitude and phase of a disturbance based on the position error between the position of the head and a target position. The feedforward control system computes a disturbance compensation value for eliminating the disturbance to output the disturbance compensation value to the feedback control system based on each detection result of the amplitude and the phase.

Abstract: A hard disk drive that redefines a notch filter of the drive. The update process may include initially disabling all notch filters and inducing a seek operation of the disk drive heads. A position error signal is read during a settling time of the seek operation and processed to determine the frequency of the signal. The frequency is selected as a resonant frequency if the error signal magnitude exceeds a threshold value. The notch filter is then redefined in accordance with the selected resonant frequency. The controller may also perform a routine to determine whether the resonant frequency is above or below a Nyquist frequency. Unlike prior art techniques, the method disclosed can obtain the resonant frequency without sweeping the excitation signal of the disk drive voice coil motor.

Abstract: A method for writing servo information onto a disk of a hard disk drive with a servo writer. The method includes writing a plurality of spiral servo signals with a head. The spiral servo signals are used to write servo patterns using at least one timing window. The timing window is adjusted using a position error signal generated from the spiral servo signals. The adjusted timing window is then used to write servo patterns onto the disk. Adjusting the timing window compensates for irregularities in the spiral servo signals.

Abstract: The present invention is a method and apparatus for positioning a read/write head in a hard disk drive. The method comprises providing a disk having a at least one side with a plurality of tracks, where each of the tracks has a servo field with servo bits. The servo bits are read to provide a position signal for positioning a read/write head. The method determines a difference in position between an initial and a subsequent position of the read/write head on a track, where the subsequent location occurs after the read/write head has moved one revolution from the initial position on the track. The initial and subsequent positions are offset laterally. The method generates a compensation signal based on the initial position, the subsequent position and the difference. The position signal and the compensation signal are combined to provide a compensated position signal for positioning the read/write head. Various embodiments are described.

Abstract: Methods and systems for sensing a position of a transducer head with respect to a storage medium. One method includes generating a read signal from a servo track stored on a magnetic storage medium. The servo track includes servo frames of magnetic flux transitions forming detectable servo marks, the servo marks forming a tone field of repeating servo marks oriented at a first azimuth angle and a mid-frame synchronization mark incorporated within the tone field, wherein the tone field provides a metric reference for dimensional measurements between features within the servo frame(s). The number of servo marks in the tone field of each servo frame along a longitudinal direction of the servo track before the mid-frame synchronization mark and after the mid-frame synchronization mark varies with lateral position.

Abstract: A recording/reproducing method and a recording/reproducing apparatus for magnetic tapes are provided as a recording/reproducing technique suitable for recording density enhancement of magnetic tapes. The method and apparatus are capable of correctly recording and reproducing data without causing errors even with occurrence of size changes in the widthwise direction of a magnetic tape. In the recording/reproducing method for magnetic tapes in which data tracks and servo tracks are provided, a tape width is detected and a value of the tape width is stored during data recording, and data reproduction is performed while tape tension is controlled so that the tape width during data reproduction is maintained equal to the tape width during data recording.

Abstract: The burst pattern shape in a discrete medium is set to a shape (truncated quadrangular pyramid shape) having substantially trapezoidal shapes in a track width direction and in a track circumferential direction, respectively, and a predetermined relationship is satisfied among W1, W2, Tp, and Wr where W1 represents an upper side corresponding to the surface of a convex magnetic recording layer and W2 a lower side corresponding to the lower surface of the convex magnetic recording layer in the trapezoidal shape in the track width direction, Tp represents a data track pitch of a data information recording portion, and Wr represents a read width of a magnetic head. Therefore, the burst pattern shape makes it possible to largely reduce a production load in processing and still to obtain an accurate position error signal.

Abstract: The invention provides a tape library wherein the accommodated number of cassette tapes can be adjusted freely. Where one or more expansion units are connected to a basic unit, when a transport mechanism is positioned within the basic unit, a control circuit section of the basic unit controls the position and operation of the transport mechanism with reference to a position reference point of the basic unit, but when the transport mechanism is within an expansion unit, the control circuit section controls the position and operation of the transport mechanism with reference to a position reference point of the expansion unit.

Abstract: A device streamlines air flow inside a hard disk drive with a stationary afterbody that is located adjacent to each of the disks. The device gradually expands the air flow so that the speed of the air flow gradually decreases while pressure increases. This design reduces losses in system momentum due to sudden expansion of the air in the drive. In addition, air flow moving toward the disk pack may be contracted to allow efficient energy conversion from pressure energy to kinetic energy prior to merging of the bypass air flow with the air flow among the disks. The device has a comb-like structure that is offset from the disk pack in the radial direction. The structure fulfills an aerodynamic function, reduces track misregistration, lowers overall aerodynamic dissipation, and fulfills a filtration function.

Abstract: A disk clamp of a hard disk drive installs a disk firmly for storing data using a spindle motor of the hard disk drive. The disk clamp includes a vertical pressing portion, formed along an edge portion of the disk, for pressing an upper surface of the disk in a vertical direction, a plurality of horizontal pressing portions, formed inside the vertical pressing portion to protrude downward and be inserted between an outer circumference of the spindle motor and an inner circumference of the disk, to press an inner circumferential surface of the disk outwardly, and a plurality of screw coupling holes formed inside the horizontal pressing portion, through which screws are inserted to be coupled to an upper end portion of the spindle motor. The horizontal pressing portions are formed in at least three positions in a circumferential direction at regular intervals or at four positions at an interval of approximately 90° in the circumferential direction.

Abstract: A plurality of first coil segments is formed in a space encompassed by a lower core layer, a protuberant layer, and a back gap layer, and a magnetic pole layer is deposited on the first coil segments. Ends of adjacent first coil segments are connected through the intermediary of a plurality of second coil segments formed on the magnetic pole layer so as to form a helical coil layer. The upper surfaces of the protuberant layer, the first coil segments, and the back gap layer are formed to be a continuous planarized surface. A Gd-determining layer made of an insulating material is formed on the planarized surface such that it covers the upper surfaces of the first coil segments. The Gd-determining layer serves also as an insulating layer that isolates the first coil segments and the magnetic pole layer.

Abstract: A thin-film magnetic head includes a lower core layer; a recording core formed on the lower core layer and exposed at a face surface facing a recording medium, the recording core including a gap layer, an upper pole layer, and optionally, a lower pole layer; an upper core layer magnetically coupled to the upper pole layer; and a coil. A tip surface of the upper core layer at the face surface is set back from the face surface in the height direction, and the tip surface is an inclined surface or a curved surface in which the depth gradually increases from the track width direction. A method for fabricating a thin-film magnetic head is also disclosed.

Abstract: Heat assisted magnetic recording systems with composite recording films are disclosed. The magnetic recording films include superparamagnetic nanoparticles dispersed in an antiferromagnetic or ferrimagnetic matrix. The matrix provides antiferromagnetic coupling with the superparamagnetic nanoparticles, and minimizes exchange interactions between adjacent nanoparticles.

Abstract: An actuator arm assembly of a hard disk drive. The assembly includes a flexure that is attached to an actuator arm and a head coupled to the flexure. The head is coupled to a pre-amplifier circuit of the drive. The head is also electrically grounded through the flexure and the actuator arm. To improve the reliability of the ground path the flexure has a spring that is contact with a slot of the actuator arm. The spring provides a ground path from the head to the actuator arm.

Abstract: An example of a multi-layer structure which may be used for supporting a transducer includes a support layer and an etch stop layer formed from a refractory metal on the support layer. A first electrically conducting layer of copper may be positioned on the etch stop layer. A dielectric layer may be provided on the first electrically conducting layer. A second electrically conducting layer of copper may be provided on the dielectric layer. The dielectric layer is positioned between the first electrically conducting layer and the second electrically conducting layer. The second electrically conducting layer may include a plurality of separate electrically conducting lines.

Abstract: A ramp member is supported on a flying slider in a load/unload mechanism of a recording medium drive. The flying slider receives a lift at its air bearing surface based on airflow generated along the moving recording medium. The flying slider flies above the recording medium. The flying height of the flying slider can be controlled with a higher accuracy in the same manner as a flying head slider utilized to read and write data from and into the recording medium. The slope of the ramp member on the flying slider can accordingly be kept at a predetermined level above the recording medium with a higher accuracy. Even if the extent of the slope is reduced, the load bar is allowed to reliably contact the slope. This leads to expansion of the data zone on the recording medium.

Abstract: Apparatus and method for grounding a flexure of a head suspension assembly to a moving support such as an actuator arm or an E block close to a preamplifier, write driver or other wiring such as a flexible circuit located on the moving support in a disk drive assembly, including connecting a metal substrate layer of the flexure to a ground on the moving support closely adjacent the preamplifier or flexible circuit to minimize ground loop interference with signals on the traces. The invention includes a variety of arrangements to secure the metal substrate layer to the moving support.

Abstract: A magnetic recording head includes an upper shield layer, a lower shield layer, a magnetoresistive film interposed between the upper shield layer and the lower shield layer, and a pair of leads electrically coupled to the magnetoresistive film, in which a pair of side shield layers constituted by portions of the upper shield layer is formed on both sides of the magnetoresistive film, and a spacing between each side shield layer and the magnetoresistive film is formed to be narrower than twice of a spacing between the upper shield layer and the lower shield layer, thereby a side reading amount can be made smaller than a conventional side reading value determined from the spacing between the upper and lower shield layers and a magnetic spacing between the head and a medium.

Abstract: A reproducing head of a thin-film magnetic head incorporates an MR element, a pair of bias field applying layers located to be adjacent to the side portions of the MR element, and a pair of electrode layers that are located on the bias field applying layers and overlap the MR element. The electrode layers each have a first layer that is laid over part of the top surface of the MR element via a protection layer, and a second layer that overlaps the first layer. In the method of manufacturing the reproducing head, after forming the protection layer on an element-to-be film to make the MR element, a first electrode-to-be film to make the first layers is formed continuously without interposing a step of exposing the protection layer to the air.

Abstract: A transducing head includes a multilayered magnetoresistive sensor having an air bearing sidewall opposite aback sidewall and a first sidewall opposite a second sidewall. A specular layer is positioned on at least one of the air bearing sidewall, the back sidewall, the first sidewall, and the second sidewall. Each sidewall is transverse to the layers of the magnetoresistive sensor.

Abstract: A first free magnetic layer, a second free magnetic layer, a lower pinned magnetic layer, and an upper pinned magnetic layer are formed of magnetic materials whose ? values are suitably set so that the resistances for up-spin conduction electrons of all the magnetic layers become lower than those for down-spin conduction electrons when the magnetization of a free magnetic layer is changed to exhibit a lowest resistance. The magnetic detecting element exhibits an increased change in resistance per area.

Abstract: A magneto-resistance effect element is provided and includes a lower conductive layer, a pattern provided thereon and made up of a fixed layer having a pinned orientation of magnetization, a first non-magnetic layer provided on the fixed layer, a free layer provided on the non-magnetic layer and having an orientation of magnetization varied by a magnetic field applied thereto, a first magnetic layer provided on the free layer; and a vertical bias layer, provided on the first magnetic layer, for applying a magnetic field to the first magnetic layer, and a sense current for detecting a change in electrical resistance of the non-magnetic layer flows substantially in perpendicular relation to the non-magnetic layer. The pattern is buried in an insulation layer with the vertical bias layer of the pattern being exposed on an upper surface of the insulation layer.

Abstract: The invention relates to a magnetic recording head comprising: a bottom shield; a top shield; and AMR device with MR and SAL separated by a thin insulating layer; a first insulting gap layer between said bottom shield and said AMR; a second insulating gap layer between said AMR and said top shield; a conductive layer contact at one end region of said MR and SAL. Furthermore, magnetic recording heads with GMR device free of electric-pop noise also are disclosed.

Abstract: An electrostatic discharge (ESD) protection circuit for an integrated circuit (IC) is disclosed. The ESD protection circuit has a RC module having a resistor and capacitor connected in series; and a current dissipation module for dissipating the ESD, wherein the capacitor is formed by a thick native gate oxide of a transistor, and wherein the thick native gate oxide prevents leakage current formed therethrough so that to avoid leakage current through the current dissipation module during a normal operation of the IC.

Abstract: A present invention provides a PDA with built-in voltage protection, comprising a main device, a socket, and a voltage protection module. The main device performs necessary data processing. The socket connects to an adapter. The voltage protection module is coupled between the main device and the socket, wherein the voltage protection module receives an input voltage from the adapter and allowing the input voltage to be applied to the main device when the input voltage is between a preset maximum voltage and a preset minimum voltage.

Abstract: A circuit configuration has a first semiconductor switch and a first protection circuit. The protection circuit has a second semiconductor switch whose load path is connected between a control terminal and a load path terminal of the first semiconductor switch. The second semiconductor switch is switched on by a comparator circuit, in each case for a predefined time period, in dependence on a comparison between a load path voltage and a reference voltage, or between a load path current and a reference current.

Abstract: A solenoid drive circuit includes a control circuit which comprises a detector with a resistor for discerning current flow therethrough to produce electric signals that correspond to level of current flow through a solenoid connected to the resistor; an amplifier for amplifying the electric signals from the resistor; and an integrator for integrating the amplified output from the amplifier.