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Movements, leaders, victories and the continuing fight for equality.
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Movements, leaders, victories and the continuing fight for equality.
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Meet the people whose lives, choices and achievements shaped the journey.
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Wilmington, North Carolina once had a thriving Black middle class and an elected interracial government. In 1898 white supremacists used violence to overthrow that government, kill Black residents and drive many others from the city.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
In electronics, a ferrite core is a type of magnetic core made of ferrite on which the windings of electric transformers and other wound components such as inductors are formed. It is used for its properties of high magnetic permeability coupled with low electrical conductivity (which helps prevent eddy currents). Moreover, because of its comparatively low losses at high frequencies, ferrite is extensively used for the cores of RF transformers and inductors in applications such as switched-mode power supplies and ferrite loopstick antennas for AM radio receivers.
A ferrite bead – also called a ferrite block, ferrite core, ferrite ring, EMI filter, or ferrite choke – is a type of choke that suppresses high-frequency electronic noise in electronic circuits. Ferrite beads employ high-frequency current dissipation in a ferrite ceramic to build high-frequency noise suppression devices.
Plated-wire memory is a variation of magnetic-core memory developed by Bell Laboratories in 1957. Its primary advantage was that it could be assembled by machine, which potentially led to lower prices than magnetic core, which was almost always assembled by hand. Instead of threading individual ferrite cores on wires, plated-wire memory used a grid of wires coated with a thin layer of iron–nickel alloy (permalloy). The magnetic field normally stored in the ferrite core was instead stored on the wire itself. Operation was generally similar to core memory, with the wire itself acting as the data line, and the magnetic domains providing the individual bit locations defined by address (word) lines running on either side of (and perpendicular to) the data wire. Early versions operated in a destructive read mode, requiring a write after read to restore data. Non-destructive read mode was possible, but this required much greater uniformity of the magnetic coating. Improvements in semiconductor RAM chips provided the higher storage densities and higher speeds needed for large-scale application such as mainframe computers, replacing previous types of memory, including both core and plated-wire memory. Plated-wire memory has been used in a number of applications, typically in aerospace. It was used in the UNIVAC 1110 and UNIVAC 9000 series computers, the Viking program that sent landers to Mars, the Voyager space probes, a prototype guidance computer for the Minuteman-III, the Space Shuttle Main Engine controllers, the KH-9 Hexagon reconnaissance satellite, and in the Hubble Space Telescope.
TIFRAC (Tata Institute of Fundamental Research Automatic Calculator) was the first computer developed in India, at the Tata Institute of Fundamental Research in Mumbai. Initially a TIFR Pilot Machine was developed in the 1950s (operational in 1956). Based on the IAS machine design, the development of the final machine was started in 1955 and was formally commissioned (and named TIFRAC, by Jawaharlal Nehru) in 1960. The full machine was in use until 1965. TIFRAC included 2,700 vacuum tubes, 1,700 germanium diodes and 12,500 resistors. It had 2,048 40-bit words of ferrite core memory. This machine was an early adopter of ferrite core memory. The main assembly of TIFRAC, which had vacuum tubes was housed in a massive steel rack measuring 18 feet x 2.5 feet x 8 feet. It was fabricated from modules of 4 feet x 2.5 feet x 8 feet. Each module had steel doors on either side for accessing the circuits. A cathode-ray tube display system was developed to serve as an auxiliary output to the computer for analogue and digital display of both graphs and alpha-numeric symbols. A manual console served as the input/output control unit of the computer. The software of TIFRAC were written in a series of commands of 0s and 1s (machine code). A British-built HEC 2M computer, happened to be the first digital computer in India, which was imported and installed in Indian Statistical Institute, Kolkata, during 1955. Prior to that, this institute had developed a small analog computer in 1953, which is technically the first computer in India.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Shirley Chisholm, elected in 1968.