Task: Question Generation
Input (English): One early attempt at lengthening the playing time should be mentioned. At least one manufacturer in the early 1920s, World Records, produced records that played at a constant linear velocity, controlled by Noel Pemberton Billing's patented add-on governor device. As these were played from the outside to the inside, the rotational speed of the records increased as reproduction progressed. This action is similar (although in reverse) to that on the modern compact disc and the CLV version of its predecessor, the Philips Laser Disc.
Output (English): What caused the constant linear velocity?