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?
One possibility I just thought of is the 24th century version of a vacuum tube system, but if that were the case I would expect them to be on key locations all over the ship (engineering, sick bay, the bridge, ready room, etc.) and I don’t think there are any others shown on the ship.