Tacktick T121 Hull Transmitter. The Speed, Depth and Compass Transducers link to the Hull Transmitter which sends the information to the Micronet Displays by wireless link. It can be sited anywhere convenient on the boat usually close to the transducers. Key Features. Only 230g (0.51lbs). 9 - 24 V external power supply .110mm x 114mm x 31mm.