The Gray Audograph was a dictation machine format introduced in 1945. It recorded sound by pressing grooves into soft vinyl discs.
The Audograph recorded on thin vinyl discs of 15cm diameter, recording from the inside to the outside, the opposite of conventional gramophone records. Unlike conventional records, the disc was driven by a surface-mounted wheel. This meant that its recording and playback speed decreased toward the edge of the disc (like the Compact Disc and other digital formats), to keep a more constant linear velocity and to improve playing time,The 78rpm Home Page - Center-Start 78s which was ten minutes. A late 1950s model which used transistors.
In 1950, Gray began to make a variant of the Audograph for AT&T, known as the Peatrophone.
References
External links Restoring Gray Audograph recordings Image of Audograph catalog