Short Access Time Research Articles

Digital Data Pattern Display System

This paper describes a data processing and display system that graphically represents digital data transmitted from a spaceborne vehicle in such a way that the operation of the payload can be rapidly evaluated. The digital data is converted to analog form and is presented in a pattern of dots and special symbols, representative of digitally coded information, in an X-Y coordinate form on a cathode-ray tube. The digital data processing system is described, but emphasis is placed on the data storage system and the attendant circuits. The storage medium used in this system is high-resolution scan-conversion tubes, which allow simultaneous write-in and readout. The data, which can be asynchronous, is read out by a high-resolution TV-type scanning and monitor system. The use of the scan-conversion tubes affords the most advantageous combination of storage capacity, storage time, short access time, and equipment economy.

Transmission of Lettuce Mosaic Virus by a New Vector, Pemphigus bursarius

Laboratory studies with the lettuce root aphid, Pemphigus bursarius (L.), and lettuce mosaic virus showed that three forms of the aphid tested were able to transmit the virus. P. bursarius was less efficient in transmitting the virus than Myzus persicae (Sulzer). The apterous root forms of P. bursarius transmitted the virus with less efficiency from foliage to foliage than they did from root to root. Sap inoculation tests using a local lesion host, Gomphrena globosa L., as an indicator, showed that less virus was present in the roots of lettuce mosaic virus infected plants than in the foliage. Transmission efficiency by the apterous viviparae did not significantly increase following a pre-access fast, but the aphids transmitted after a shorter access time. The fundatrigeniae of P. bursarius from poplar and the alienicolae from lettuce were also rather inefficient vectors of lettuce mosaic virus. However, the fundatrigeniae were superior vectors when compared with the alienicolae. A comparison of incubation periods of the virus in the plants when the virus was transmitted from foliage to foliage and from root to root showed mean incubation periods of about 7 days with foliage to foliage transmission and 15.5 days with root to root transmission.

A digital computer store with very short read time

The paper describes the principles of operation and the construction of storage units with a very short access time for reading. One form of the store which has been constructed has a capacity of 200 000 bits of permanent information and another has been built with a capacity of 100 000 bits, the whole contents of which may be changed in under one minute. The technique employed permits the construction of very large stores at low cost. Each digit cell is formed, basically, by two sets of windings which form the primary and secondary of a transformer and the two binary states are determined by the presence or absence of a piece of linear ferrite material coupling the windings. The access time is largely determined by the physical size of the store and the speed of operation of the associated circuits; a time of 100 millimicrosec is typical.

A magnetic-drum store for analogue computing

The paper describes how a conventional magnetic drum may be used in an analogue computer. The magnetic drum becomes a versatile element in this computer, giving a large storage capacity combined with a relatively short access time. Several of the important facilities obtainable by this technique are discussed.

Universal high-speed digital computers: a magnetic store

The elements and organization of an experimental magnetic storage system are described. A rotating wheel is used to give high transfer speeds and relatively short access time to data which are transferred directly to the high-speed cathode-ray tube store of a digital computer. The wheel is run in synchronism with the fundamental frequency of the computer under the control of a servo mechanism. A plated layer of pure nickel is used as the recording medium. A lowimpedance type of head combined with a new method of digital representation have been employed for the storage of data.A complete storage system of this type with a capacity of 3 000 numbers, each of 40 binary digits, has been incorporated in the Manchester University computer.