Today in History - December 29, 1891 - Thomas Alva Edison patents “transmission of signals electrically” by radio. Close to a year later, on August 9, 1892, he received a patent for a two-way radio.

Also on this date in 1952, the first transistor hearing aid went on sale by the Sonotone Corporation.  This hearing aid was much larger than the miniature ones today as it was a hybrid of analog and digital technologies,  weighing 3.5-oz, measuring 3 inches and costing around $300 (which would be over $1500.00 today). Still it was a big improvement over the large amplifying horns and other devices used previously. Alexander Graham Bell was originally working on hearing aids for people with deafness when he invented the telephone using such a horn in 1876. Edison’s phonograph, invented in 1877, also used such a horn to amplify and broadcast sound.

For more information, see the Engineering Pathway’s resources on Edison and radios or hearing aids. For curricular resources, browse our resources for persons with disabilities, or visit the Electrical Engineering Education or Engineering Diversity community sites.