The resulting reader was a mechanical tour-de-force, combining five MICR readers with a large rotating drum that forced checks dumped in the top to come out the bottom single-file.
This process allows depositing customers the ability to capture front and rear images of checks along with their respective MICR data for those being deposited.
The routing number is part of the magnetic ink character recognition, or MICR, line at the bottom of your check, which also includes your account number.