The Sectronic Mk III movement differs from the Mk I and Mk II in that it is a moving magnet balance, not a moving coil. This considerably simplifies the electrical circuitry and therefore the production complexity and costs. Many parts are moulded from plastic, and the electronics are all mounted on one small circuit board, including the trigger and drive coils for the balance. The hands are driven by an inverted Sully escapement. The clocks normally run from one 1.5 volt LR14/MN1400/C size cell.