hi ron, there are 2 control sections in every hot tub. one is called the topside controller. this is the owners interface to various functions. bubbles, jets, temp control, time of day, etc. this unit consists of an lcd driver, an eprom and a pic microcontroller. the second control board is called the power board. it consists of the relays that control the pumps, it consists of lots of pc814 optos, triac for blower motor, it also supplies power to the topside. it also has a pic micro. no eprom. it has a heater element that heats the water(draws tons of current 20 plus amps). thats pretty much it.