Sonotone 1010

The Sonotone 1010 hearing aid, introduced December 1952, was the was the first commercial product to use transistors, which had been invented five years earlier in 1947.Fildes, Jonathon (2005-11-15). "Switching on the digital world". BBC News. p. 1. Retrieved 2007-11-16.

It was a hybrid design, using two miniature vacuum tubes as input stages and a single transistor as the output stage; this was required because the transistors at the time produced too much electrical noise. Even using one transistor considerably extended battery life, lowering the operating cost of the unit. As transistors improved, this model was replaced by all-transistor hearing aids.