It is a 4-wire ultrasonic signal converter. Combined with the flow sensors OPTISONIC 3000 and OPTISONIC 3000 District
Heating it forms the OPTISONIC 3400 ultrasonic flowmeter for inline flow measurement of liquids as well as the OPTISONIC 3400 District
Heating ultrasonic flowmeter for use in heat metering applications.
Together with the OPTISONIC 4000 HT and HP flow sensors it forms the ultrasonic flowmeters OPTISONIC 4400 HT and OPTICONIC 4400 HP  for inline flow measurement of high temperature and high pressure liquids.