Abstract: A system is provided for continuously monitoring and displaying temperature levels of a patient which is particularly adapted to indicate the ovulation activity of a female through monitoring the temperature variations of the body of the patient during the menstrual cycle. The system includes a transducer, such as a thermistor, for producing an output voltage in accordance with the temperature sensed, a voltage controlled oscillator for producing an output whose frequency varies in accordance with the output voltage of the thermistor, and a binary coded counter, controlled by the system clock, which produces a four-bit digital output representative of the measured temperature. The output of the counter during each cycle is stored in a shift register and after N cycles, an analog voltage representative of the arithmetic average for the N cycles is compared with an analog voltage corresponding to the output for the N + 1 cycle.