Patent GB-1495835-A (GB)
Title: Arrangements for storing information in the form of single wall magnetic domains
IPC: G11C19/08
Filed: 1975-02-19
Abstract: 1495835 Repertory diallers; magnetic storage arrangements WESTERN ELECTRIC CO Inc 19 Feb 1975 [20 Feb 1974] 7093/75 Headings H4K and H3B A repertory dialler employs a magnetic store which is powered over the telephone line, the store being characterized in that the telephone numbers are stored in the form of single wall, magnetic domains i.e. in the form of so called magnetic bubbles. A circuit, Fig. 13, for deriving power supply voltages of 76V, 26V and - 2À5V required by the dialler from the line voltage at + γ, - γ comprises six component circuits. Multivibrator 260 and regulator 261 operate to supply a regulated voltage to a parallel arrangement of three capacitor circuits 262A-262C with circuit 263 acting as a switching circuit such that the detector B switches on when capacitor 279 reaches a sufficient voltage to power the circuit. Devices 269, and D2 are constant current diodes, the diode 269 being utilized to enable the circuit to operate at different line voltages and impedances caused by different line lengths. Arrangement of the store, Figs. 1 and 3.-On depression of a digit push button or a digit selection using a dial, a corresponding number of magnetic bubbles are generated along the section 13 of a major bubble path MP of the store using alternate storage locations. In addition a queuing bubble is generated in expansion stage 17 and a marker bubble is generated in the horizontal section of spur path 18, the distance between the point of generation of the marker and queue bubbles and the bubble detector 32 and annihilator 41 being related to the digit selected. The push button depression causes the application of a rotating magnetic field in the plane of the layer 11 which in known manner causes bubble movement along the bubble paths. The movement is halted when the queue bubble in expander 17 reaches a magneto resistive detector 32, at which time the marker bubble has reached point 40 (Fig. 3) of the horizontal section of spur path 18. Selection of a further digit causes the process to be repeated with the marker bubble for the previous digit being stepped from point 40 to annihilator 41. After selection of the final digit, either a last number dialled to a repertory push button is depressed to cause the marker bubble at 40 of the last digit to be replicated into section 42 of spur path 18. In addition the contents of the last number dialled minor loop ML11 or one of the repertory minor loops ML1-ML10 are prepared for annihilation. The rotating magnetic field is again applied and as the marker bubble in section 42 of spur path 18 is stepped along path 18 into the major path MP and eventually to the expander 17 and bubble detector 32, the contents of the corresponding minor loop are stepped past an access port situated at the point of adjacency of the minor loop and upper horizontal section of the major path, where they are annihilated. Detection of the marker bubble at 32 causes the access port of the minor loop to be switched to a replication mode, and as the bubbles representing the telephone number pass the access port, the bubbles are replicated into the minor loop, the bubbles of the number into the major path then continuing along the path to the expander 17 and the detector, their detection causing the corresponding number of pulses to be sent to the telephone line. The minor loops each have an odd number of storage locations the number of locations being such that at least two empty (zero) locations are left between the end and beginning of a number, these zeros then acting as a start code. This code is important when a stored number is read-out because in a read mode of the store, replication for a minor loop into the major path can commence at any position in a digit of a telephone number. Bubbles reaching the detector 32 are hence ignored until the start code is detected. The number of storage locations between the generator 13 and the access port to loop ML11 is  sufficient to allow an eleven digit number to be stored and to be stepped towards the loop during the annihilation of the loop contents such that the first bubble does not reach the access port until after annihilation is complete. Similarly the number of locations between point 40 and the detector 32 via paths 42 and MP is such as to allow an eleven digit number in a minor loop to be completely annihilated. A complete description of all the control circuitry of the store is given in the Specification. CMOS integrated circuits are employed.