The three companies that supply most of the nation’s election equipment and ballots will deploy thousands of technicians Tuesday to head off problems that disrupted some primary elections earlier this year. Missing equipment, programming errors and too few voting machines delayed election results in some states. In others, confused poll workers and voters hesitated to use new touch-screen machines. Three companies–Election Systems & Software, of Omaha, Sequoia Voting Systems of California, and Diebold Election Systems of Ohio–say everyone involved has learned from the mistakes.