The HB TS3 Switch will allow connecting 2 xducers to one head unit and then switch between the 2 ...
HB has discontinued the HB TS3 Switch but it can still be purchased thru some marine retailers ... (I think it will show back ordered if trying to purchased thru HB) ...
https://www.humminbird.com/Products/TS3/
Be sure to change the "Connected Transducer" selection under the Sonar tab to HB 83/200kHz when using only the US2 such that the imaging transmitter (DI or SI if capable) is not firing to an open wire channel ...
Rickie

