| 摘要 |
814,942. Inductors and transformers. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Aug. 24, 1955 [Aug. 31,1954], No. 25302/54. Class 38 (2). [Also in Groups XIX, XXXVIII and XXXIX] By changing the reluctance of a magnetic core the direction of the flux therein is determined without destroying the flux. The direction of the voltage induced in a read-out coil linked with the core indicates the direction of the flux. The reluctance is changed by a coil linked with only a part of the cross-section of the core or by a current in the core itself. Bi-stable magnetic stores.-As shown in Fig. 1, a coil 15 is passed through a hole 14 in the ferrite core 11 of a bi-stable magnetic storage device and the reluctance is increased by one or more pulses from an interrogating signal source 16. A gate in the sensing means 19 is closed by the source 16 when the pulse in winding 13 induced by the leading edge of the interrogating pulse has had time to die away. If the source 16 produces a series of pulses, the sensing means may include an integrating circuit to provide a sustained output potential on lead 20. The interrogating source may produce an alternating current of frequency f1 instead of pulses. The sensing means 19 is then tuned to the second harmonic frequency 2 f1. Reversal of the flux in the core shifts the phase of the second harmonic output by 180 degrees, the shift being detected by a known phase-sensitive rectifier circuit. The core shown in Fig. 2 comprises two concentric rings 22, 23 in contact with each other except in a small region 24. Similar windings 25, 26 on the two rings provide a flux circulating around the gap. The reluctance of the core shown in Fig. 4 is changed by a current in the core between two conductors 40, 41. Magnetic tape and drum records; reading heads.-By detecting the direction of the flux in a reading head 10a, Fig. 3, of low retentivity, binary data recorded on a magnetic tape or drum 35 can be read whilst the head is fixed relative to the tape or drum. The effect of the earth's magnetic field can be eliminated by recording each item twice and using two pick-up heads. The two recording patches 81, Fig. 7, are of mutually reversed polarity and the recording heads A, B are connected so as to form an astatic pair. Specification 752,415, [Group XXXVIII], is referred to. |
