The 939 programming functions are for adjusting the tip temperature and the tip temperature offset. The attached link will download a pdf copy of the 939 Instruction Manual. Page 7 gives instructions for changing the tip temperature and page 10 gives instructions for offsetting the tip temperature (Adjusting the Tip Temperature). The 939 was designed with a lock out feature requiring a card (p/n B2052) to unlock the station before you can change the temperature. You must have the card to access the temperature adjustment feature. You can purchase a replacement card at www.HakkoUSA.com if necessary.