Automatic pool cleaning apparatus

An apparatus for automatically cleaning submerged surfaces, such as the bottom and side walls of a swimming pool. In a preferred embodiment, the apparatus includes onboard sensors, and an onboard processor (preferably, a microprocessor) which controls operation of the apparatus in response to status information supplied from the sensors. Preferably, the apparatus has an onboard watertight battery and an adjustable inlet nozzle size, and includes left and right track treads which are controllable to cause the apparatus to turn or rotate (clockwise or counterclockwise), or translate in a forward or reverse direction, on a horizontal or vertically inclined submerged surface. A transmission assembly is provided for each track tread, including a cam wheel and a cam follower connected thereto within a sealed control assembly, and a shift link extending through a seal in the control assembly. Each shift link has an end connected to one of the cam followers and another end connected to a gear assembly, for shifting the gear assembly into a forward or a reverse gear. The apparatus preferably includes Hall effect transducers (with associated permanent magnets) and a microprocessor mounted within a sealed control assembly. The microprocessor is programmed to execute a selected one of a number of cleaning programs (thereby entering a selected operating mode) in response to exposure of the Hall effect transducers to a magnetically permeable card punched with specially arranged holes, or a card with a magnetically permeable insert molded within it.