If you received your transponder from an agency other than Metro (i.e. your transponder does not have the Metro logo on the back), you must always use the same transponder with your CAV when driving in the Metro ExpressLanes. You are prohibited from using this transponder in any other vehicle when accessing the Metro ExpressLanes.
If you received your transponder from Metro or one of its retailers (i.e. your transponder has the Metro logo on the back), you are not required to keep the same transponder in your CAV at all times.