This is a sound powerd telephone and it is one of the primary lines of communication within the ship. The device in the upper right is a growler, you select the party you want to call on the selection switch and turn a handle on its far side (unseen) it then makes a growling sound at the station you are calling, notifying them of the incomming call. This was one of the circuits I serviced while serving in the Navy on a similir ship.