The room-sized machine that secured Churchill's calls

A closer look

What started as a boring way to cram more phone calls onto expensive copper wires ended up securing the most sensitive conversations of World War II. Homer Dudley invented the Vocoder at Bell Labs to break human speech down into electronic parameters, transmitting the data instead of the actual audio wave. While the telecom cost-savings were neat, the military realized this synthetic robot voice was perfect for encryption. They beefed it up into SIGSALY, a massive, room-sized machine that scrambled the Vocoder's output with white noise on phonograph records. It allowed Churchill and FDR to chat securely across the Atlantic without the Nazis understanding a single synthetic syllable.