Hello wasn’t used as a greeting until many years later when the telephone was invented. Inventor Thomas Edison is given credit for suggesting the use of hello as a standard greeting when answering a telephone. Edison’s competitor, Alexander Graham Bell, had his own idea for a proper telephone greeting.
The series that began the franchise, Mighty Morphin Power Rangers (an American adaptation of the 1992 Japanese Super Sentai Series, Kyōryū Sentai Zyuranger), began broadcasting as part of the Fox Kids block of programing that aired on the Fox network. It lasted for three seasons (from 1993 to 1996).