Overview
This lecture covers the history, development, technology, and impact of the electrical telegraph, the first practical electrical telecommunications system used worldwide from the 1840s to the late 20th century.
Introduction to Electrical Telegraphy
- Electrical telegraphy transmits text messages over wires using electric signals between telegraph offices.
- It was the first major electrical engineering application and transformed long-distance communication.
Early Experiments and Invention
- Early concepts (1753–1809) used multiple wires for each letter or chemical reactions to signal messages.
- Notable early inventors include Le Sage, Smmering, Salva Campillo, and Ronalds.
- In 1820s–1830s, advances in electromagnetism and relay development led to practical telegraph designs.
Key Systems and Innovators
- Cooke and Wheatstone's 1837 needle telegraph used multiple wires and needles to indicate letters.
- Samuel Morse and Alfred Vail developed the Morse telegraph (1837), using coded rhythmic electric pulses and Morse code.
- The Morse system became the international standard by 1865.
Commercial and Technical Evolution
- Telegraph networks expanded rapidly across Europe and North America from the 1840s.
- Submarine cables allowed intercontinental communication from the 1850s.
- Improvements included chemical telegraphs, printing telegraphs, and automated systems like Wheatstone’s ABC and Baudot code.
- Teleprinters and Telex finally automated telegraphy through much of the 20th century.
Social and Economic Impact
- Telegraphy revolutionized railway safety and national/international communication.
- Enabled instant messaging (telegrams), transforming business, journalism, and military operations.
- Played a crucial role in time signal transmission for longitude determination and scientific collaboration.
Decline and Legacy
- The telephone and later the Internet gradually replaced telegraphy for public and business use.
- Western Union’s strategic errors contributed to the telegraph’s decline in the US.
- Today, “telegraph” services rely on computer networks rather than dedicated wires.
Key Terms & Definitions
- Telegraph — Device for long-distance text communication using electric signals.
- Morse Code — Encoding system using dots and dashes to represent letters and numbers.
- Teleprinter — Automated device for sending and receiving typed messages over telegraph lines.
- Telex — Automated telegraph exchange network using teleprinters.
- Submarine Cable — Underwater cable enabling telegraph communication between continents.
- Relay — Electrical switch used to renew and transmit weak telegraph signals.
Action Items / Next Steps
- Review Morse code alphabet.
- Study a timeline of telegraph technological developments.
- Understand differences between needle, armature, and teleprinter systems.