User:Edison/Inductive train telegraphy

Inductive train telegraphy or the "grasshopper telegraph" was a system of wireless telegraphy developed  in the early 1880's which allowed Morse Code signals to be sent back and forth from  moving trains to fixed telegraph systems, by means of electrical induction. It was a precursor to radio communications. The sending unit on the train used a battery, Morse key for the transmission of dots and dashes, a vibrator to make and break the circuit rapidly at an audio frequency, an induction coil to step up the voltage, and an insulated metal plate on the roof of the train car to transmit the signal to telegraph wires on poles parallel to the tracks. An ordinary telephone receiver was in the circuit between the battery and the train wheels, which in turn connected the signals to the tracks. Signals could be heard after passing through over 500 feet of air. Thomas Edison and William Wiley Smith developed the "grasshopper" system of inductive train telegraphy, based on Edison's experiments in inductive telegraphy of the late 1870's and early 1880's and Smith's 1881 U.S patent#247,127. Edison began experiments on wireless telegraphy by the early 1880's, and filed for a patent on the device 23 May, 1885. He and Ezra Gilliland received U.S. patent 350,235 on 5 October 1886. It was installed and tested on the Lehigh Valley Railroad in 1886. Following lawsuits regarding priority of invention, Edison joined with inventor Lucius Phelps, who had received U.S patent 307,984 in 1884 for his owns own inductive train telegraph system and tsted in it January 1885, to form the Consolidated Railroad Telegraph Company on April 4, 1887. On 6 October, 1887, an inductive railway telegraphy system (combining the innovations of Thomas Edison, Lucius Phelps, Willoughby Smith, and Ezra Gilliland) was operated successfully from a train of the Lehigh Valley Railway travelling 60 miles per hour, and over a distance of 25 feet. Edison did additional research in wireless telegraphy, obtaining another patent in 1891. He sold his patents on wireless telegraphy to Marconi in 1904. Besides Phelps, Granville Woods was another contemporary who independently experimented with and patented a system of inductive wireless train telegraphy.

Legacy of inductive railway telegraphy
For reliable operation, it was desirable to have insulated metal panels on the roofs of several adjacent train cars. This could be a problem in the operation of trains. The railway inductive telegraphy system was used by trains of the Lehigh Valley Railway for several months in 1887-1888. The grasshopper system of inductive wireless telegraphy was used successfully to communicate between a train stuck in a snowdrift in the Great Blizzard of 1888 and the outside world, one of the earliest instances of wireless telegraphy being used for emergency communications. The use of the grasshopper system for inductive train telegraphy was abandoned, and replaced in the 20th century by train telegraphy and telephone communications using radio waves.