In Voyager’s transporter room, there is an alcove on the side, and embedded in the wall is what appears to be a small transporter pad. I don’t believe anyone is ever shown interacting with this, so there’s no definitive explanation for what it is. Assuming it is what it appears to be, what would be the purpose of a very small transporter like this?
It’s a replicator. The transporter waveguides at the back are common in Intrepid-class replicators. You can see a smaller one in Janeway’s quarters.
Under the replicator is supposed to be an equipment storage locker (according to the Star Trek Fact Files and the USS Voyager Illustrated Handbook), so it’s likely for creating extra away team equipment. It may also be for food - we see a food dispensing slot in the USS Enterprise transporter room in TOS: “Tomorrow is Yesterday”.