A landing signal officer or landing safety officer (LSO), also informally known as paddles (United States Navy) or batsman (Royal Navy), is a naval aviator specially trained to facilitate the "safe and expeditious recovery" of naval aircraft aboard aircraft carriers. LSOs aboard smaller air capable ships that launch and recover helicopters are informally known as deck. Originally LSOs were responsible for bringing aircraft aboard ship using hand-operated signals. Since the introduction of optical landing systems in the 1950s, LSOs assist pilots by giving information via radio handsets.