<image>As shown in the figure, $$A$$ and $$B$$ are points on the hyperbola $$y= \dfrac {k}{x}$$. Perpendicular line segments are drawn from points $$A$$ and $$B$$ to the x-axis and y-axis, respectively. Let $$S_{1}$$, $$S_{2}$$, and $$S_{3}$$ denote the areas of the three rectangles in the figure. Given that $$S_{3}=1$$ and $$S_{1}+S_{2}=4$$, find the value of $$k$$.