A HB DI unit can use a dual xducer setup (2d xducer and a DI xducer) by using a TS3 Transducer Switch and make the needed changes in the "Connected Transducer" menu each time you want to see the 2d or the DI..This is only possible because the 800, 900 and 1100 series DI units all have the standard 200/83kHz 2D sonar capability (the 300, 500 and 700 series DI units do not).