Alexander Graham Bell’s patent for the telephone was issued on March 7, 1876,
by the U.S. Patent Office. Three days after receiving his patent. Bell succeeded
in getting his invention to work when he accidentally spilled some acid. He spoke
the famous sentence, “Mr. Watson…Come here…I want to see you”. His assistant Thomas Watson, listening at the receiving end of the device in an adjoining room,
heard the words from Bell clearly and rushed to his aide.

 
Thomas A. Watson

The master copy of Bell’s patent for the telephone