Editing Delay-line memory (section)

===Magnetostrictive delay lines===
[[File:Torsion wire delay line.jpg|thumb|Torsion wire delay line]]

A later version of the delay line used [[wire|steel wires]] as the storage medium. Transducers were built by applying the [[magnetostriction|magnetostrictive effect]]; small pieces of a magnetostrictive material, typically [[nickel]], were attached to either side of the end of the wire, inside an [[electromagnet]]. When bits from the computer entered the magnets, the nickel would contract or expand (based on the polarity) and twist the end of the wire. The resulting [[torsional]] wave would then move down the wire just as the sound wave did down the mercury column.

Unlike the compressive wave used in earlier devices, [[Torsion (mechanics)|torsional]] waves are considerably more resistant to problems caused by mechanical imperfections, so much that the wires could be wound into a loose coil and pinned to a board. Due to their ability to be coiled, the wire-based systems could be as long as needed, so tended to hold considerably more data per unit; [[kilobit|1&nbsp;kbit]] units were typical on a board only 1&nbsp;[[square foot]] ({{nobr|~30 cm × 30 cm}}). Of course, this also meant that the time needed to find a particular bit was somewhat longer as it travelled through the wire, and access times on the order of 500&nbsp;microseconds were typical.

[[File:Highgate Wood 100 micro second delay line store.JPG|thumb|100-microsecond delay-line store]]

Delay-line memory was far less expensive and far more reliable per bit than [[Flip-flop (electronics)|flip-flops]] made from [[vacuum tube|tubes]], and yet far faster than a [[latching relay]]. It was used into the late 1960s, notably on commercial machines like the [[LEO&nbsp;I]], [[Highgate Wood Telephone Exchange]], various [[Ferranti]] machines, and the [[IBM 2260|IBM 2848 Display Control]]. Delay-line memory was also used for video memory in early terminals, where one delay line would typically store 4 lines of characters (4&nbsp;lines × 40&nbsp;characters per line × 6&nbsp;bits per character = 960&nbsp;bits in one delay line). They were also used very successfully in several models of early desktop [[electronic calculator]], including the [[Friden, Inc.|Friden]] EC-130 (1964) and EC-132, the [[Olivetti]] [[Programma&nbsp;101]] desktop [[programmable calculator]] introduced in 1965, and the Litton [[Monroe Epic]] 2000 and 3000 [[programmable calculators]] of 1967.