What was Emile Berliner's connection to the Bell Telephone Company?

Emile Berliner was a German-born American inventor who became interested in the then new audio technology of the telephone and phonograph, and invented an improved telephone transmitter (one of the first microphones) which was acquired by the Bell Telephone Company. Berliner subsequently moved to Boston in 1877 and worked for Bell Telephone until 1883, when he returned to Washington and established himself as a private researcher. Emile Berliner invented the microphone. How did he become famous though? I don't get it!