The telegraph revolutionized long-distance communication in the 19th century, allowing near-instantaneous messaging across vast distances. It used electrical signals to transmit coded messages, laying the foundation for modern telecommunications. This page provides a simple explanation of how telegraphs worked, their range, key milestones, and data speed equated to modern baud rates.
The basic electric telegraph consisted of a transmitter (key), receiver (sounder or printer), wire line, and battery. Pressing the key completed an electrical circuit, sending current through the wire to the receiver, which produced clicks or marks. Messages were encoded in Morse code—short/long pulses (dots/dashes) for letters/numbers. The first sounders only clicked, producing short/long sounds that operators interpreted by ear. It took significant skill to decode clicking accurately, especially at high speeds—operators trained for years to "read" the rhythm of clicks reliably. Later models added paper tape or ink printers for visual records.
Early telegraphs spanned a few miles; by mid-1800s, land lines reached hundreds of miles with relays every 20-50 miles. Transatlantic cables (1866) extended to thousands of miles, but signals weakened over distance, requiring repeaters. Limitations: Weather disrupted overhead wires, submarine cables were expensive/fragile, and human operators slowed throughput.
Telegraph speed was measured in words per minute (WPM); skilled operators sent 20-40 WPM (average word 5 letters + space). Equated to baud rate (bits/second): Morse code averaged ~25 baud at 25 WPM (each dot/dash ~1-3 bits equivalent, plus pauses). Modern comparison: 300 baud modems were ~12x faster than a fast telegraph operator. Telegraphs were slow by today's standards but instantaneous compared to mail.
The telegraph shrank the world, enabling global news and business. It led to telephone, radio, and internet. By 1950s, it declined with voice phones, but its code and infrastructure influenced modern data transmission. The decommissioning of telegraph lines in the mid-20th century marked the end of an era, as automated telephone and telex systems replaced manual operators and clicking sounders.