Frequency-Independent, Self-Clocking Encoding Technique and Apparatus for Digital Communications

This document describes a patent for a digital encoding technique that enables synchronous transmission of data between devices such as controllers and disk drives. The method uses bipolar (positive and negative) pulses of fixed duration. By comparing a bit with its successor, the encoder determines the pulse pattern; if consecutive bits are the same, a compensating pulse of opposite polarity is injected to ensure the signal has no DC component. This design facilitates AC coupling, reduces ground loop issues, and is frequency-independent, allowing receivers to decode the data without needing to know the specific transmission rate of the sender. The document includes technical descriptions of the encoding circuitry, multiplexer logic, and decoding apparatus, as well as an adaptation for fiber-optic implementations.