A radio terminal device realizing reduced power consumption and prompt detection of detection object by using a first sensor and a second sensor whose ON/OFF states are opposite and whose operations are synchronized. When the first sensor detects a detection object, the first output voltage level is changed. When a processor detects the change of the output voltage level as an interrupt signal, the drive voltage level of the first sensor is switched to low and the drive voltage level of the second sensor is switched to high. Moreover, when the second sensor detects a detection object, the output voltage level of the second sensor is changed. When the processor detects the change of the output voltage level as an interrupt signal, the drive voltage level of the second sensor is switched to low and the drive voltage level of the first circuit is switched to high.