An anonymous reader points to this explanation of a brain-machine interface for real-time synthetic speech production
, which has been successfully tested in a 26-year-old patient. From the article: "Signals collected from an electrode in the speech motor cortex are amplified and sent wirelessly across the scalp as FM radio signals. The Neuralynx System amplifies, converts, and sorts the signals. The neural decoder then translates the signals into speech commands for the speech synthesizer."