A magnetoacoustic keyboard

Abstract

A keyboard which minimizes electrical interconnections and is naturally suited for microprocessor applications has been developed using a magnetoacoustic delay line. The delay line utilizes a 2 µmeter magnetostrictive 50:50 NiFe plating on a 125 µmeter BeCu<inf>2</inf> wire, fabricated with a circumferential easy axis. The wire is formed in a serpentine shape to pass under all the keys. The keys contain low-intensity molded permanent magnets which can rotate the magnetization from the circumferential direction. An interrogation current pulse in the wire generates acoustic waves under each depressed key, which propagate to a sense coil where the torsional waves are sequentially sensed. Each interrogation pulse from the microprocessor produces a list with the status of every key. © 1979 IEEE