This is a 2-wire 4-20mA level transmitter consisting of a transducer and an amplifier connected via a 6-core vented cable.
The transducer is a pressure sensitive silicon micro strain gauge sensor mounted in a glass to metal seal. The sensor is protected by an isolation diaphragm, electron beam welded to the transducer housing, with an oil filling between the sensor and the diaphragm. Pressure changes in the front of the diaphragm will bring a resistance change in the Wheatstone bridge of the transducer. Wheatstone bridge will be transmitter to the amplifier as a change in the electrical signal.