The TTT shares all of the extensive features of the TST except that it has no internal transducer. Instead, the TTT offers not one but two external transducer interfaces allowing any two transducers to be simultaneously connected. Selection between the transducers is made by a two way switch in the side of the instrument case. Any transducer from Norbar's "SMART" range and most mV/V calibrated transducers from Norbar or other manufacturers can be connected to the TTT. The "SMART" feature means that once a transducer has been connected, the instrument will automatically recognise calibration details such as mV/V output, serial number and capacity.