Yep, that is the doorbell. It is a wireless unit similar to what you can buy a Lowes, Home Depot, etc. Now you need to find the receivers/noise makers inside the rig. My '03 40e came with one receiver on the wall under the dining/computer table. About 3 years after we bought the rig I found another receiver under the bottom drawer below the cooktop ...it did not have batteries in it. I moved it to a new location under a drawer in a cabinet in the bedroom. The receivers take D Cell batteries. I don't know if the button itself has a battery in it, but I would guess it has to.
Our button has stuck a few times ...last month someone rang the bell and it just kept going on and on and on. I had to pry the button out with a screw driver, then used some spray lube to keep it from sticking again.
Just to warn you ...these doorbells also go off on their own on rare occasions. High tension power lines seem to do it. A neighbor with a similar door bell might set yours off when theirs is pushed. And on two occasions our doorbell has gone off while we were driving through a stop-light controlled intersection !!
