Apparatus for the electrical stimulation of nerves
First Claim
1. Apparatus for the electrical stimulation of nerves comprisingstimulus means for generating an electrical stimulus of alternating polarity and varying periods, which is non-zero for most of the duration of most of the said periods,an electrode for location in a position where a nerve can be stimulated, andcharge control means for ensuring that the net charge applied to the electrode is zero in each of successive intervals substantially throughout stimulation, each interval having a duration equal to an integral number of said periods not greater than three.
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Accused Products
Abstract
Apparatus primarily for stimulating the auditory nerve in the vicinity of the cochlea of deaf persons to give a sensation indicative of the pitch of speech is described. The stimulus which is in the form of an alternating current of varying period dependent on the pitch of speech is applied to an electrode positioned in the vicinity of the cochlea. The current is non-zero for most of the duration of most stimulation periods and in order to elicit a stable auditory sensation d.c. baseline fluctuation is prevented by the use of a controlled current generator. The period of speech sounds is found using a specially devised circuit and a voltage related to the frequency of such sounds is determined by a period-to-voltage converter and a reciprocal circuit, this voltage being supplied as a control signal for the current generator. An alternative microcomputer version is also described. In order to give an indication of the presence of voiceless sounds, a detector capable of distinguishing between voiced and voiceless sounds is also included together with a noise source which is coupled to the stimulation electrode when the detector indicates the presence of voiceless sounds.
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Citations
17 Claims
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1. Apparatus for the electrical stimulation of nerves comprising
stimulus means for generating an electrical stimulus of alternating polarity and varying periods, which is non-zero for most of the duration of most of the said periods, an electrode for location in a position where a nerve can be stimulated, and charge control means for ensuring that the net charge applied to the electrode is zero in each of successive intervals substantially throughout stimulation, each interval having a duration equal to an integral number of said periods not greater than three.
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9. Apparatus for determining the voice period of voiced sounds comprising
a transducer for providing an electrical signal representative of sounds, a logarithmic amplifier coupled to the transducer by way of a low-pass filter, and peak detection means coupled to the amplifier output and arranged to respond to the first peak in each voice period of the sound representative signal to generate an output pulse each time the said signal indicates that the vocal cords of a speaker making the voiced sounds have closed.
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14. Apparatus for distinguishing between voiced and voiceless speech sounds comprising
means suitable for coupling to a sound transducer for determining respective intervals between signal reversals in the transducer output signal, and means for indicating the presence of voiceless sounds when, in each of a group of pairs of successive said intervals, the durations of the intervals are both shorter than a predetermined interval.
Specification