Richardson's handbook of projection (1930)

MANAGERS AND PROJECTIONISTS 987 Disc Record Recording THE disc record method of recording, which is employed by the Vitaphone Corporation, among others, is very different from the sound-on-the-film method. The "disc record" is really nothing more or less than an enlarged phonograph record, made somewhat differently and with extreme care, playing from inside to outside instead of outside to in, as with phonograph records, and with special markings on both record and film, and a geared synchronization of the record-carrying turntable with the motion picture projector mechanism to insure a continuance of synchronization between sound and action, once it has been established by proper use of the aforesaid markings. These records rotate, both in recording and in reproduction, at 33j^ revolutions per minute. The method of recording is exactly the same as with sound-on-the-film up to the instrument actually inscribing the sound record upon the disc. The sound is picked up by a microphone, and transformed into electric current, as already described. It then passes through the amplifiers, as set forth, but there the similarity ceases. First, however, a bit of explanation concerning the groove on a phonograph record. The general idea is that the record consists of a series of indentations made by the needle point in the bottom of the groove. Put in another way, it is popularly believed that the record consists in or of differences in depth of the bottom of