This series of affordable, lightweight dopplers is designed to meet routine fetal exam requirements. SonoTrax Basic is a high performance fetal doppler with FHR detection and digital LCD display. SonoTrax Pro adds the convenience of a backlight display, battery status display and audio playback. These models have audio output, which can be connected to an earphone or recorder. The units also can be operated with 4MHz or 8MHz waterproof probe for vascular diagnoses.