Gray Audograph

The Gray Audograph was a dictation machine format introduced in 1945.

It recorded sound by pressing grooves into soft vinyl discs.

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,[3] which was ten minutes.

[4] In 1950, Gray began to make a variant of the Audograph for AT&T, known as the Peatrophone.