Abstract: An apparatus and method for the controlled dynamic braking of a DC motor in a tape transport device are provided. A PWM state device includes a plurality of state transition paths, each path having an initial state, representative of a tape profile, including a predetermined range of tape velocities, relative amounts of tape on each reel and an initial tape tension, and at least one subsequent state. When a low power event is detected, one of the state transition paths is selected, based upon a current tape profile, and an associated PWM signal is transmitted to the motor. An energy storage device provides power to the PWM state device during the low power event. The PWM signals follow the selected transition path to modulate the current generated by the motion of the motor and thereby create a decelerating force while substantially maintaining the initial tape tension.

Abstract: A method for calibrating a tape transport servo system for a tape drive is disclosed. The tape reel motors are excited when the tape drive is not being controlled by the tape transport servo system. Then, calibration data is collected for the motor torque, motor friction, DAC offsets, and pulse width modulator control signal timing.

Abstract: A handhole cover includes a body adapted to cover a handhole. The body has a front surface, a rear surface, and a peripheral edge. Engagement members protrude rearwardly and outwardly from the rear surface adjacent to the peripheral edge. The engagement members are adapted to engage a peripheral edge of the handhole and are spaced about the peripheral edge to provide a secure engagement of the body in the handhole. At least one of the engagement members is a rotatable locking member having a helical engagement surface. The rotatable locking member is selectively rotated between a locking position and a release position.

Abstract: A method for calibrating a tape transport servo system for a tape drive is disclosed. The tape reel motors are excited when the tape drive is not being controlled by the tape transport servo system. Then, calibration data is collected for the motor torque, motor friction, DAC offsets, and pulse width modulator control signal timing.

Abstract: Air entrainment effects are avoided in a bi-directional, reel-to-reel tape transport in which magnetic tape can be moved in either of two opposing directions for data recording thereon. Control of tape position is implemented in a servo algorithm that uses tachometer inputs to determine parameter values for generating reel motor drive currents. A fine-line tachometer is mounted on each of two reels in the tape drive and multiplexing selects the fine-line output from the tachometer on the reel supplying tape for use in the servo algorithm. At least one of the tachometers is preferably of the type which generates an index line once each revolution of the motor to which it is mounted. This tachometer is coupled to the reel to which the tape is initially threaded and the index line is used to indicate that the motor is at a predetermined threading position for this operation.

Abstract: The present invention provides a method and system for generating a position error signal from a signal produced by a read element detecting a track comprising two harmonically unrelated patterns positioned parallel to each other on a magnetic media. The apparatus of the present invention produces a delayed signal from the read signal produced by the read element. The read signal is multiplied with the delayed signal to form a product signal. The product signal is integrated to produce a position error signal, wherein changes in the position error signal that are proportional to changes in position of the read element over the two patterns positioned parallel to each other on the magnetic media.

Abstract: Apparatus and method for controlling a reel-to-reel tape drive so that its performance characteristics are optimized to best suit the operational mode or availability of a host system by modifying tape speed adaptively according to predetermined conditions sensed during processing of data (i.e., while the tape is in motion). For example, tape might initially be fed at a high speed suitable for archiving; but if more than a predetermined number of "backhitches" (overruns of the interblock gap, IBG) occur during processing of a preselected number of successive blocks of data, the host will cause tape speed automatically to be reduced to a lower rate. This lower rate will enable the tape to stop in the IBG and is therefore suitable for intermittent processing.Preferably, before reducing speed during write operations, appropriate signals are generated at the host to command an increase in the IBG from a normal distance to a larger distance if backhitches exceed said preselected number.