The Invention
The patent, US388803A, granted to Granville T. Woods of Cincinnati, Ohio, on August 28, 1888, is for a significant improvement in induction telegraphy for railways. Induction telegraphy allows for communication between a moving train and a stationary station without a physical wire connection.
Woods’s goal was to enhance the efficiency of this system. He wanted to get a stronger electrical signal from a single, fixed conductor line along the railway, thereby “economizing” on the amount of expensive wiring needed.
Key Features:
- Single-Wire System: Unlike some other systems that used a double-conductor arrangement, Woods’s invention is designed to work with a single, fixed line-conductor (1) laid on or near the ground.
- Unique Induction Coil: The most innovative part of the invention is the induction coil that is carried by the train. Instead of a straight core, this coil is wound on a soft iron bar that is bent into a spiral or waved line (2). This bar is shaped like a rectangle but with its long sides bent to run parallel to the track.
- Increased Induction Effects: Woods’s genius lies in his understanding of electrical and magnetic principles. He explains that by bending the core into a spiral, he brings the coil’s wire into “approximate parallelism” with the fixed conductor. This alignment causes the “amperean or magnetic currents” of both conductors to coincide, resulting in a stronger induced electrical impulse and a much clearer signal.
- Comprehensive Communication System: The patent details an entire communication system, including:
- Sending Apparatus: A station-side system that uses a “pole-changer” to send a series of rapid current reversals down the line. This prevents static buildup and creates a powerful, clear signal.
- Receiving Apparatus: A car-side system that includes a telegraphic relay (14) and a printing or registering device (17) to record messages. It also has a condenser (13) to handle the rapid incoming signals and a telephone receiver for audio.
Significance of the Invention and Inventor
Granville T. Woods was a brilliant African American inventor who revolutionized railway and electrical technology. His work in induction telegraphy was a major step toward creating safe and efficient modern rail systems.
- Pioneer of Wireless Communication: Before Marconi and the invention of radio, Woods was a pioneer in wireless communication. His system of induction telegraphy was a practical and effective way to send messages to and from moving trains, a critical need for railway safety and operations. It allowed train dispatchers to communicate with engineers, preventing collisions and improving scheduling.
- Technological Ingenuity: This patent is a superb example of Woods’s deep knowledge of electrical science. He wasn’t just building on existing ideas; he was applying fundamental physics principles to create a more efficient design. His spiral-core induction coil was a clever and elegant solution to the problem of a weak signal.
- Overcoming Barriers: As an African American inventor in the late 19th century, Woods faced immense challenges, including racial prejudice and legal battles with other inventors who tried to claim his work. Despite this, he held over 60 patents and established himself as a leading electrical engineer. His railway telegraphy system, in particular, was so successful that it was adopted by major railway companies, solidifying his reputation and paving the way for future innovators.
