Is there a list of companies who make optical scan voting machines?

Factual Questions
1

i live in a county that is switching to Optical Scan voting machines. I am curious how many companies make these machines. Is there a list somewhere of voting machine companies?

I am also wondering why one machine might be better than another, is one safer against fraud, cost effective, user friendly and whatever else goes into making these decisions by our trusty local officials. :dubious:

Thanks
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2

Check here for a list of voting machine manufacturers:

http://www.ifesbuyersguide.com/browse.php?product_category_secondary_id=22&&&start=0

The main companies, from looking around, appear to be Diebold, Sequoia, Hart Intercivic, and ES&S.