Do EHS cables work with expansion modules (also called SideCars)?

Answer-- MAYBE.

Does the Expansion Module have an EXT or EHS port? If so, try plugging the part of the hookswitch that would regularly plug into the EHS or EXT port of the Yealink phone into that. That may work for remote answering and ring detection... but it may not. Sometimes adding a sidecar will cause the EHS cable not to be able to pick up and hang up the phone properly and/or you may not get ring detection!

If it doesn’t, you’re out of luck! The Expansion Module needs the phone’s EHS/EXT port and if there isn’t another one available the hookswitch has no place to go. Sorry friends!