Here is the patent for that product.  Perhaps this will shed some light on how it works.  I&#x27;ll see myself out. <a href="http:&#x2F;&#x2F;www.google.com&#x2F;patents&#x2F;US5590093" rel="nofollow">http:&#x2F;&#x2F;www.google.com&#x2F;patents&#x2F;US5590093</a>