Some of my initial attempts at using potrace to produce electronic components in SVG format for use with Inkscape can be seen at the URL below. The embedded figures are in SVG format so you will need a browser with an SVG plugin or save the figures and open them in Inkscape.

http://www.isu.mmu.ac.uk/~za9ra01/svgstuff/svg-libs.html

I have another Inkscape SVG file containing a collection of various transistor symbols which I have not put up on the web yet.

Thanks

Bill Peel