Here is a pic of the fan timer. there are 3 buttons. the top button increases fan running time the middle lowers fan running time the bottom button is what controls which fan you are running. the pic says "F4", so that means that matt has pushed the lower button 4 times until the display says "f4". Now he can use the upper 2 buttons to adjust fan running time. at its max, this timer will be able to run 8 computer fans (just like what we use on the accumonitor humidity canisters. you can control them in sets of 2.