[TeX][1] can be used to generate publication-quality schematics.  [Here are some examples.][2]

> [CircuiTikz][3] is a set of LaTeX macros designed to make it easy to draw electrical networks in scientific publications. It provides a convenient syntax based on to-paths to place the various components.

![enter image description here][4]

Or generate them in PostScript in conjunction with TeX?  I think these are similar enough to combine in one answer.

> [pst-circ][5] is a PSTricks package to draw electric and electronic circuits. It can be used either with TeX or LaTeX.

![enter image description here][6]


  [1]: http://en.wikipedia.org/wiki/TeX
  [2]: http://www.texample.net/tikz/examples/area/electrical-engineering/
  [3]: http://web.archive.org/web/20090605170624/http://home.dei.polimi.it/mredaelli/circuitikz/examples.html
  [4]: https://i.sstatic.net/b2aC3.png
  [5]: http://pstcirc.free.fr/index.html
  [6]: https://i.sstatic.net/Hb77h.png