NIST scientists have figured out that Morse code may get through poor
transmission conditions when voice does not.

"...first responders may be able to receive and see simple patterns—like
Morse code—from a survivor repeatedly turning a radio or phone on and off,
in cases where the signal was too weak to receive audible voice messages."

http://www.nist.gov/public_affairs/r...ion_dcconv.htm

73 de Jim, N2EY