Channel capacity (baud rate)

Late 19th century telegraph engineers sought to improve communication speed by designing machines automating lower-level signaling, separating human input from physical signal generation.

“Baud rate” (named after Émile Baudot) measures symbol transmission speed—the number of signaling events (secondary symbols) per second, independent of information content per symbol.

Émile Baudot designed a multiplex telegraph system deployed in 1874, using five keys played as “chords” to represent letters, revolutionizing telegraph speed and efficiency.

Channel capacity represents the fundamental maximum rate at which information can reliably transmit through a communication channel, formalized by Claude Shannon in his 1948 information theory.

Encoding efficiency measures how closely a communication system approaches the theoretical information rate limit—maximizing information content per transmitted symbol.

Baudot’s five-bit encoding assigns 32 possible key combinations to letters, numbers, and control characters, establishing fixed-length binary character representation.

Information rate (bits per second) provides a universal metric measuring communication speed applicable to any system—human, animal, or alien—independent of physical implementation.

Automated telegraph systems establish a two-level symbol hierarchy: primary symbols (letters) that humans manipulate, and secondary symbols (electrical pulses) that machines generate.

Automated telegraph machines require precise clock sources generating consistent pulse timing, enabling reliable high-speed operation and multiplexing.

Telegraph technology evolved from manual Morse systems (~40-60 words/minute) through automated machines (hundreds of words/minute), driven by relentless demand for faster communication.

Baudot’s multiplex system pioneered time-division multiplexing (TDM)—enabling multiple operators to share single telegraph wire through synchronized time-slot allocation.