Shaft 8 rotates about fixed axis A-A and carries rigidly mounted round gear rack 1 and worm 5 which mesh with gears 2 and 6. Gears 2 and 6 rotate about fixed axes B and C. One addend a is entered by shifting shaft 8 axially so that rack 1 turns gear 2 until the value of addend a is indicated on scale 3. In this axial motion of shaft 8, worm 5 turns gear 6 through an angle equal to the angle of rotation of gear 2. The second addend b is entered by turning shaft 8 until the value of addend b is indicated by pointer c on dial 4 which is keyed to the shaft. When shaft 8 is turned, gear 2 remains stationary and gear 6 turns an amount corresponding to the second addend. The sum a+b is read off on scale 7.
$2830$WG,MO$