Ocean Gate Titan missing: Titanic submersible has seven backup systems to return to the surface

Rescuers were racing against the clock Wednesday to find a tourist submersible with five people on board that vanished on its descent to the century-old wreck of the Titanic.

In addition to an international array of ships and planes, an underwater robot had started searching in the vicinity of the Titanic and there was a push to get salvage equipment to the scene in case the sub is found.

CBS News journalist David P O G U E, who travelled to the Titanic aboard the Titan last year, said the vehicle uses two communication systems: text messages that go back and forth to a surface ship and safety pings that are emitted every 15 minutes to indicate that the sub is still working.