Time Frame
( If Applicable )

 1. Phonograph invented,
     Thomas Alva Edison

 1877

 cylinder type phonograph

 2. AC electric power invented,
     Nikola Tesla

1888

 alternating current power

 3. Wireless telegraph invented, 
     Guglielmo Macroni

1895 

 wireless transmission

 4. LP phonograph record

1948

 33 1/3 LP phonograph record

 5. 45 RPM phonograph record

1949

 45 RPM records

 6. Stereophonic recording

1958

 two channel stereo recording

 7. Digital compact disc invented,  
     Phillips Electronics and
     Sony Corp.

1980

 digital compact disc concept

 8. Commercially available compact
     disc

1982

 commercially available compact 
 disc equipment