Record Playback

Record playback was developed in the late 1940s, roughly contemporaneous with numerical control, as a competing approach to machine tool automation. In record playback, the machinist performed the operation by hand while the machine recorded every movement — position, feed rate, spindle speed, the thousand micro-adjustments an experienced machinist made without conscious deliberation. The recording was then played back, reproducing the operation with mechanical precision. The knowledge stayed in the machinist's hands. The automation was real, but it did not require the transfer of productive knowledge to a separate programming department. Noble's archival research established that record playback was cheaper, often technically superior for complex contours, and systematically suppressed — making it the canonical case of an alternative design rejected for political rather than technical reasons.