they would normally have 3 settings: 1 = on 0 = off clock symbol = timed.
to set timer put in clock symbol position and push in the small black pins on the outer of the clock for the times you would like it to be on. ie if you want 6-8 in the morning then put all the pins between 6-8 in the down position and as long ast he timer moves then it should come on ok
andy
October 2010