George A. Campbell
Born Nov 27 1870 - Died Nov 10 1954
Loading Coil
Electric Wave Filter
Patent #: 1,227,113

Inducted 2011

George Campbell was a leader in applying mathematical methods to the problems of long-distance telephony. His most important contributions were to the theory and implementation of loading coils and the first wave filters. In 1897, Campbell went to work for AT&T in Boston. Both of his innovations gave significant competitive advantage for his employer, as they permitted AT&T to carry multiple telephone messages on a single line over longer distances. Campbell’s method for transmitting telephone signals over much greater distances was made possible by the insertion of loading coils into the line at carefully calculated intervals. Around this same time, Michael Pupin, a physicist at Columbia University, patented a similar system.

Invention Impact

An important result of his work on loading coils was that Campbell began work on filtering in 1910. AT&T was attempting to use the same wires for many telephone conversations simultaneously; the filters were needed for reasons of privacy, as well as intelligibility, so there was no crosstalk between channels. Since the filter designs allowed multiple conversations to be sent over the same wire, they were of great economic value and resulted in substantial savings in cable installation costs.

Inventor Bio

George Campbell was born in Hastings, MN. He attended MIT and Harvard. Campbell received many awards including both the IEEE Edison Medal and the IEEE Medal of Honor.