Patent GB-936720-A (GB)
Title: Improvements in or relating to devices for use as electric circuit elements
Inventor: WILLIAMS MICHAEL
IPC: G11C19/08
Filed: 1959-10-27
Abstract: 936,720. Magnetic storage apparatus. GENERAL ELECTRIC CO. Ltd. Jan. 26, 1961 [Oct. 27, 1959], No. 36417/59. Class 40 (9). [Also in Group XXXV] A shifting register comprises a strip F, Fig. 1, of magnetic thin film having either a longitudinal or a transverse easy direction of magnetization, the registered information being characterized by the magnetic polarities of discrete regions of the strip and the polarity pattern being shifted by a four-stage cycle of currents applied selectively to adjacent conductors C1-Cn. The magnitude of the current applied to any single conductor is insufficient by itself to reverse the magnetic state of the associated film region except when an adjacent region is already of the opposite magnetic polarity, in which case flux reversal takes place by reason of domain boundary growth. Initially the regions of the film may be all magnetized in an upward (transverse) direction representing a binary zero, as shown in Fig. 3 (a). During the first stage of an operating cycle, alternate conductors C1, C3, C5 are energized and produce magnetic fluxes having the directions shown in Fig. 2, the digits 1, 2, 3 ... identifying the film sections associated with respective conductors C1, C2, C3 ... During this stage of energization a conductor D is pulsed to produce a downward acting field if a "one" is to be stored, and the combined currents in C1 and D together cause the magnetization of film portion 1 to be reversed as shown in Fig. 3 (b). The second stage of operation involves energization of alternate conductors C2, C4 ... so that the flux pattern shown in Fig. 2 is moved by one section to the right. As the section 2 is influenced by the current in conductor C2 and by the adjacent downward field of section 1, its magnetization is reversed as shown in Fig. 3 (c). Similarly for the third and fourth stages the conductors C1, C2, C3 ... are so energized that at each stage the energization pattern shown in Fig. 2 is again moved stepwise to the right. During the third stage conductor D is pulsed in a "zero " sense so that the magnetization of film section 1 becomes upward, and the resulting film flux pattern is produced as shown in Fig. 3 (d). Thus a binary one digit is stored in the form of two adjacent sections magnetized in the downward sense and moved by one section to the right for each stage of energization. The energization of the last conductor Cn for each operating stage is in the same downward direction as in Fig. 2, so that when the stored digit is advanced from the position shown in Fig. 4 (a) to that in Fig. 4 (b), three sections of the film acquire the same downward polarity. The abrupt transistion induces an output pulse in a pick-up conductor P which is applied by external circuits to a clear conductor E, this conductor current restoring these three sections to the initial state as shown in Fig. 4 (c). The arrangement may be modified for parallel read out by providing a conducting loop enclosing the whole assembly which, when energized, establishes a field parallel to that due to currents in the conductors C1, C2 ... The whole strip is then remagnetized in the same zero sense, additional pick-up conductors being provided. Alternatively a suitable selection of the conductors C1, C2 may function also as such conductors under the control of external gates. Non-destructive read-out is also possible. In a further modification the input is in parallel form and output is in serial order, pulses of sufficient magnitude to reverse the magnetic state of selected sections being applied to an appropriate group of conductors C1, C2 ... In order to increase the margin between the magnetic field strength sufficient for domain boundary growth, and that required for domain formation, a high frequency electromagnetic field having a frequency about ten times that of the pulse current supplied to conductors C1, C2 ... may be applied by positioning the arrangement within a single layer solenoid formed by winding a conductor of strip form. The easy direction of the film may in an alternative construction lie along the strip F, in which case the conductors C1, C2 ... and E cross the strip at right angles and the conductor D lies parallel to the length of strip.