http://www.cs.uiowa.edu/~jones/voting/colloq/
Jones Talk, Slide 4

A Brief History of Voting Technology

• Lever Voting Machines
  -- First use, Lockport, New York, 1892.
  -- Universal in US urban areas by 1930's.
  • Closing the curtain on the voting booth cocks mechanism.
  • Pulling levers does nothing.
  • Opening curtain resets levers and increments registers.
  • Each register is an odometer mechanism.
  • Printer-pack allows hard copy output.
  
  -- Weakness: Recount is impossible
  -- Weakness: Thousands of moving parts

  4 digit wheels per register.
  3 carry propagate wheels per register.
  3 ratchet, pawl and spring per register.
  several hundred registers.

  -- Weakness: Inscrutable mechanism.

  We give our trust to the service technicians, the only ones who ever see what's inside the sealed box!

  -- Strength: Nothing subjective!
  -- Strength: Interlock mechanism prevents overvotes.
  -- Strength: Secret and private.

  The booth is private enough to change clothes in, but the sound of pulling a lever has been exploited!