Abstract
As a result of the development of radio apparatus and of new types of vacuum tubes, it became possible to devise stimulators having desirable features impossible to inductorium or neon tube stimulators, i. e., greater range of frequency of stimulation, greater range of intensity of each shock, and methods for recording the frequency of the stimulation. Many instruments, incorporating some or all of these features, have been devised, outstanding examples being those of Scheminzky, 1 Schmitt, 2 Nicolai, 3 and Bouman. 4 Although these instruments can be considered as great improvements over earlier types, they all have one or more of the following undesirable features: (1) large, complicated and expensive, (2) operate on batteries, (3) unwanted and irregular leakage currents, and (4) the wave form of the stimulating current is not independent of frequency.
A recent instrument which is especially noteworthy for its portability is that devised by Cullen. 5 The attached signal magnet, however, always vibrates at a frequency of 60 times per second and so provides no means of indicating the frequency of stimulation. Furthermore, after having used this particular instrument the authors have found that the high amperage delivered to the signal magnet considerably shortens its life when the ordinary classroom type is used. Another undesirable feature is the presence of “stray charges in the instrument” which renders it unfit for precision work.
The authors have designed a portable (operating on 110 volts, A.C.) and inexpensive stimulator which does not have the disadvantages discussed and enumerated above.
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