The Manhattan Signal can refer to one of two things:

  • A cellphone-like device created by Dan Dreiberg to summon Dr. Manhattan from anywhere in the world. Due to Manhattan's particular view of time and space, he will answer this call literally two seconds before the device is actually activated. It has been very useful for Dan and the other Watchmen.
  • The original Manhattan Signal, which appeared just once during the Five Minutes to Midnight arc. It was a large, blue-bulbed searchlight stationed on top of the White House, with a piece of black metal resembling Dr. Manhattan's hydrogen symbol on it. It would shine into the night sky whenever the President needed to speak directly with Manhattan. The light was destroyed when the Owl Ship crash-landed on top of the White House at the beginning of the arc.