The Lithium Battery required for the correct operation of the RF542 Remote Temperature Monitor is a Xeno AA Lithium Cell, model XL-060F. This cell can be obtained from most battery specialists or direct from Comark, order RF542BATT.
The use of any other type of 3.6V Lithium cell may not provide you with the normal battery life and correct operation of the RF542 Remote Temperature Monitor might be affected.