Coding schemes for acoustic delay line data collection system

Abstract

A magnetoacoustic system adapted to use as a keyboard can employ a serpentine acoustic delay line passing under a number of transducers which are activated simultaneously with a current pulse through the wire. Magnets adjacent to the wire generate magnetoacoustic pulses along the wire which arrive sequentially at a sensor at one end of the line. For each key on a keyboard at least two magnets are associated with each key position with one magnet affixed in position and one reciprocably movable towards and away from the wire in a response to actuation of the key. The magnet which remains close to the wire is used to provide a 'location' signal indicating the location along the delay line provided by the wire by producing an acoustic pulse for that point on the wire for each clock pulse of current which passes through the wire. The second magnet located adjacent to the first magnet generates a pulse simultaneously with the other magnets when the current pulse passes through the wire, but it is delayed by the physical displacement along the wire, so it is received at a different time than the pulse from the other magnet. The data pulse can follow or precede the location pulse so long as the presence of one or both can be readily decoded. A three magnet key arrangement can be employed where it is desired to be able to use three positions per key.