The GFC 300 is a 4-wire ultrasonic signal converter. Combined with the flow sensors OPTISONIC 7000 and OPTISONIC 7000 Biogas it forms the OPTISONIC 7300 and OPTISONIC 7300 Biogas ultrasonic flowmeters for inline flow measurement of gases and biogas. Together with the OPTISONIC 8000 flow sensor it forms the OPTISONIC 8300 ultrasonic flowmeter for inline flow measurement of steam and high temperature gases.