The name Signal Tower comes from the signalling apparatus installed atop of the tower building that was used to communicate between the shore staff (the Master Of The Tender) and the keepers of the lighthouse. An identical set of signalling apparatus is installed atop the lighthouse itself.
The name "Signal Tower" is derived from the signaling equipment installed on top of the tower structure that facilitated communication between shore staff (the Master Of The Tender) and lighthouse keepers.  A matching set of signaling devices is also mounted on top of the lighthouse.