Abstract: Positioning of a tape head relative to a magnetic tape may be improved through accurate measuring of magnetic tape position error. The tape head includes at least one read module having two servo read elements. A head control detects the presence of corresponding synchronization fields passing the servo read elements. The elapsed time between the detected synchronization fields is determined. Tape skew is calculated based on the elapsed time. Tape position error calculation may be further improved by including another servo read element on either a second read module or a write module. Tracking information read from two servo read elements scanning the same servo stripe is used to calculate the offset between a read module and the write module.

Abstract: A servo track writer head writes servo tracks on a data storage tape with increased accuracy. The servo track writer head includes a leading writer for each servo track. Each leading writer writes a synchronization field on the tape. The servo track writer head also includes a sequence of trailing writers for each servo track. Each trailing writer produces at least one trailing field on the tape a fixed distance behind the synchronization field. The servo track writer head also includes one timing writer. Each timing writer writes a timing field on the tape at a timing distance in the tape direction from each of the synchronization fields. The servo track writer head also includes a sequence of timing readers corresponding to each timing writer. The number of timing readers in the sequence is equal to the number of trailing writers in the sequence of trailing writers.

Abstract: A servo-controlled recirculating automatic document feeder (RADF) includes a plurality of independently driven document transport devices. A picker mechanism separates documents in seriatim from a stack. An entry turnaround transport device buffers and delivers picked documents to a platen transport device for exposure. After exposure, the document is transported along a simplex or duplex path for duplex or simplex copying. The document is then buffered in an exit turnaround transport device and is subsequently returned to the stack. Each transport device is independently driven by a motor and a closed-loop servo. A common reference oscillator generates source signals for the servo-loops. A microcomputer operates on the source signals and generates reference signals for driving the transport devices.

Abstract: A sheet registration apparatus for positioning sheets in a registered position on a work surface such as the document platen of a convenience copier/duplicator machine. The apparatus includes a bidirectional servo-controlled sheet transport for conveying the sheet over the work surface. A sheet sensing device is disposed within the path of sheet travel. A controller monitors the sensing device and activates a position control routine following the occurrence of a predetermined level change in the signal generated by the sensing device. At the end of the position control routine, the transport is stopped thereby positioning the sheet in the registration zone. The apparatus enables sheet registration for a machine operating in a duplex and/or simplex mode. The apparatus further enables registration at any point on the document platen.

Abstract: A device for feeding sheets from a supply station aligning the sheets in an X, Y and .theta. coordinates and then gating the sheet into a work station such as the transfer station of a copier. The device includes a pair of independently servo-controlled motors disposed on opposite sides of the sheet. Each motor drives a nip roller which transports the copy sheet. Sensors are disposed to generate signals representative of sheet position in the X, Y and .theta. coordinates. A controller uses the signals to adjust the angular velocity of the motor so that the sheet is squared and is gated onto the work station. The sensors and controller are utilized to measure different parameters associated with the sheet.