there is shown a graphical representation of a cycle of the biphasic bbt curve of normal women which bi phasic curve includes two phases repectively designated by l the former half of a period namely a low temperature phase and h the latter half of a period namely a high temperature phase also the cycle can be divided according to the possibility of pregnancy into three stages early stage 1 or preovulation safety stage middle stage 2 the possible stage of pregnancy wherein the day designated by the abruptly sharp increase following a decreasing curve is the date of ovulation and late stage 3 or post ovulation safety stage 1 a single chip micro computer containing a microprocessor and memories a peripheral devices including and electronic body temperature detector with an analog digital convertor a keyboard for data entry a lcd display with a dot matrix and seven segment portions and the driving circuit thereof and a melody generator etc 2 a power supply system consisting of a charging device rechargeable batteries and a reminding device for recharging controlled by software program the complete system block diagram is shown in fig2 which is is described in detail hereafter this section employs a single chip micro computer with low power consumption as the memory and processing unit for data and employs the input keyboard which will be mentioned about hereafter in 1a and the electronic body temperature detector which will be mentioned about in 1b hereafter for inputting data and the dot.