Wire delay-lines were developed as a memory device for storing digital information in computers. Their operation is based on the fact that sound waves travel more slowly than electrical impulses. Electrical signals are converted to sound waves by magnetic coils at one end and sent down the wire, usually made of nickel. These signals are reconverted at the far end to electrical signals. By recirculating the signals continously the device stores information and acts as a memory. Wire delay lines were used until the late 1950s.
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