| Synthetic Thermoplastic ResinsMicrophones took over from acoustical horns, and lo and behold the development the modern 78-rpm electric phonographic amplified player, a motor-driven turntable that incorporated a record-changing device, a cartridge, and loudspeakers. These records were originally made of shellac and later of synthetic thermoplastic resins with a playing time of about 4 minutes, which became standard. ...... More on Lee de Forest in History of Vinyl Part 5 |
