Mass production technique of sound recorded sheet by magnetic contact printing

The authors have developed an industrial duplicating machine for prerecorded sound sheet by magnetic contact printing process. The main advantages of the process are its simplicity and high speed. The apparatus is free from complicated moving head mechanism and adjusted amplifiers. Duplication is performed by keeping slave sheets close contact with master sheets, and applying 50 Hz magnetic field. By this process about 5,000 copy sheets that have good sound quality almost comparable to that of direct recording, are able to be printed from one master sheet, and the duplicating capacity of a machine is around 1,000,000 sheets per month.