To connect 2 xducers to 1 head unit you would need the HB TS3 Switch (which supposedly has been discontinued) ...
https://humminbird.johnsonoutdoors.c...S3%20Switch%20
HB website allows adding the HB TS3 Switch to the cart but you should call to make sure (because it was reported discontinued) ...
Some dealers may carry the HB TS3 Switch ...
-----
The picture on the HB website is misleading ... The HB TS3 Switch is basically a Y cable with a 12v toggled relay at the "Y" ... The Pic only shows the included 12v selectable toggle ... It doesn't show the Y cable ...
Rickie