Patents Assigned to Thorn Emi Datatech Limited
  • Patent number: 4897738
    Abstract: A circuit for generating frequency-modulated signals for data to be recorded on magnetic tape has a converter to produce a control current I.sub.c for a capacitor C. A detection logic circuit senses voltage V.sub.c across the capacitor C and generates an appropriate frequency f which is fed to a charge pump, for discharging of capacitor C by a predetermined amount at a rate dependent on the frequency f. Control current I.sub.c then charges capacitor C again and the cycle is repeated. A starter circuit is also provided to ensure that the circuit oscillates on each cycle.
    Type: Grant
    Filed: February 8, 1988
    Date of Patent: January 30, 1990
    Assignee: Thorn EMI Datatech Limited
    Inventor: Michael J. Rogers
  • Patent number: 4777450
    Abstract: A demodulating circuit includes an exclusive OR gate which has a first input for a frequency modulated signal and a second input connected via a delay to a frequency dividing circuit. The second input is initially low so that an output signal is produced by the gate, enabling a pulse generator, whenever the first input is high. The pulse generator produces a train of pulses of predetermined length and frequency. These pulses are counted in a counter and the count is compared in a comparator with a predetermined number n. On the n.sup.th pulse, the comparator sets a bistable circuit which then produces an end-of-pulse-train signal, triggering the frequency dividing circuit. In response, the frequency dividing circuit produces an output signal which causes the second input of the OR gate to go high, thereby disabling the pulse generator.
    Type: Grant
    Filed: May 28, 1987
    Date of Patent: October 11, 1988
    Assignee: Thorn Emi Datatech Limited
    Inventor: Michael J. Rogers
  • Patent number: 4750682
    Abstract: A hub drive assembly includes three pairs of pivoted arms, each supporting a friction pad, which may be clamped against the inner cylindrical surface of a tape supply reel. The assembly also includes a central sleeve, rotatably driven by a motor, and a second sleeve concentric with the central sleeve. The second sleeve is provided with gear teeth, which couple with gear teeth of one arm, which in turn couple with gear teeth of the other arm of each pair. Means are also provided to rotate the two sleeves relative to each other, thereby causing rotation of the arms about their pivot points via the gear couplings, so as to bring the frictional pads into, and out of, frictional engagement with the reel.
    Type: Grant
    Filed: February 11, 1987
    Date of Patent: June 14, 1988
    Assignee: THORN EMI Datatech Limited
    Inventor: Robert V. Elliott
  • Patent number: 4749146
    Abstract: An automatically threading magnetic tape drive includes a small-flanged take-up reel and a removeable large-flanged supply reel whose diameter is greater than the center-to-center spacing of the reels. During threading, a hinged shutter is closed to provide an air-tight barrier between the reels, the supply reel lies in a region of relatively high air pressure H and the take-up reel lies in a region of relatively low air pressure L. An air-tight channel links the region H and L and tape is threaded through the channel by air flow. Tape is drawn towards the take-up hub by air flow along slots in one or both take-up flanges, and the hub surface is elastomer-coated. During normal running the shutter is opened and tape spooled on to the take-up reel may overlap the supply reel flanges.
    Type: Grant
    Filed: December 5, 1986
    Date of Patent: June 7, 1988
    Assignee: Thorn Emi Datatech Limited
    Inventors: Graham Bridger, Warwick A. Higgins