Patent GB-1223740-A (GB)
Title: Process and apparatus for information storage and non-destructive retrieval
IPC: G11B11/105
Filed: 1968-10-28
Abstract: 1,223,740. Data storage. E.I. DU PONT DE NEMOURS & CO. 28 Oct., 1968 [31 Oct., 1967], No. 50969/68. Heading G4C. Information is stored as discrete areas of differing thermally stable magnetization on a layer of hard magnetic material, and read-out non-destructively by rapidly heating to below the Curie temperature to reversibly change the magnitude of magnetization, the resulting changes in magnetic field being sensed. Bits are recorded on magnetic tape (utilizing hard magnetic material) by using a focused light (IR, UV or visible) beam from a laser or a focused electron beam, to heat the magnetic material, initially unmagnetized, to a temperature near or above its Curie point, then allowing the material to cool in a magnetic field. For non-destructive read-out, the material is heated almost to the Curie point using the laser or electron beam, the resulting magnetic field changes being detected by a conventional magnetic reading head, amplified, filtered and displayed on an oscilloscope. Modifications are: (a) the tape may be uniformly magnetized prior to recording, heating to above the Curie point demagnetizing selected areas, the subsequent cooling being in the absence of a magnetic field, (b) the tape may be uniformly magnetized prior to recording, selectively heated near the Curie point then cooled in the presence of a D.C. reverse bias field causing reverse magnetization, (c) the sensing on read-out may be done during cooling of the tape following the heating, (d) an-arc lamp may be used instead of a laser or electron beam. The recording beam may be modulated with the information. In the case of a laser, this may be done by modulating the laser excitation, or by using a Kerr cell in the output beam. Alternatively, the magnetic field, in which the tape cools, may be modulated. One embodiment uses a rotating prism to scan a laser beam across a tape moving longitudinally, the scan speed being higher during recording than during read-out, so that the laser pulses become pseudo-continuous for read-out. A biasing magnet is used during recording. As modifications, the magnetic reading head may move, the tape may be stationary, the beam may be stationary, the head may be of the composite, sequentially - addressable type. A Hall effect probe may replace the magnetic reading head. Thermal biasing may be provided by a heated plate. Besides bits, a grey scale and pictures may be recorded and read, using a lead foil mask with e.g. a letter cut in it, for recording, or using rastering. 1,223,765. Electric digital data processing. AUTOMATIC ELECTRIC LABORATORIES Inc. 6 Nov., 1968, No. 52664/68. Heading G4A. [Also in Division H4] A plurality of subsystems have access to a common memory on a multiplex system. If one subsystem has extracted data from an address in the memory, any other subsystem seeking data from that address is blocked. The invention is applied to a telephone system in which access to a destructive read-out ferrite core memory 400 of linear select type is had in inter-leaved manner by three subsystems (1) register sender apparatus 110, (2) translator and route selector 120, and (3) a system comprising trunk scanner 130, peg count section 140, or maintenance console 150. Read-out and write-in is effected over the paths shown. An address generator 500 supplies appropriate timing pulses, Fig. 2, to all blocks of common control equipment. The telephone equipment is of known type with subscriber lines, trunk lines, carrier equipment, opeators' positions, register-junctors and so on. The memory is sub-divided into rows allotted to each register-sender junctor. In each row all information relating to the progress of a call such as seizure and release of equipment is recorded. Each word-time provides for the generation of the address of a word, followed by reading the word from the memory into the appropriate read buffer, and writing the word back into the memory. As seen from Fig. 2 three word times in respect of the three subsystems are interleaved enabling the three subsystems to be operating simultaneously. In the third subsystem the trunk scanner and maintenance console have access to the memory in alternate word times. The trunk scanner during operation of a reed relay tree allots its turn to the peg-count system for registering amount of use of pieces of equipment. Because of the interleaving it is possible that the data in a memory location addressed has been read out and not yet written back. In such a case the subsystem seeking the data has its address generator stopped until the address is available. This is achieved by parity circuits comparing addresses sought by the various subsystems.