Edwin henry colpitts

(1872-1949)

Think back to when oscillators were something new to you and exciting and you will probably recall the names of two of the great telephone engineers who worked for the Bell Telephone system in the first half of this century: Colpitts and Hartley. The Colpitts and Hartley oscillators have survived long after their inventors died. Today they are transistorised and can be stabilised by quartz crystals, but they are still recognisable as the fundamental circuits invented during the First World War.

Edwin Henry Colpitts was born on January 9, 1872, at Pointe de Bute in Canada, though he was sometimes described by his contemporaries as an honorary American. A bachelors degree with honours from Mount Allison University, Sackville, New Brunswick, was followed by another at Harvard in 1896, and a masters the next year after completing a postgraduate course in physics, mathematics and engineering. He continued at Harvard for another two years as an assistant to Professor Trowbridge in the Physics Laboratory, until joining the American Bell Telephone Co in 1899.

For the next 38 years he served the Bell System in one capacity or another¹, steadily rising through the ranks until he retired in 1937 as Vice-President of Bell Telephone Laboratories. But it was up to about 1920 that most of his efforts were directly involved with hands-on engineering or scientific contributions to telephone engineering. From then until his retirement he held positions which were mostly executive, leaving little time for direct contributions to engineering. When Colpitts began his career with Bell, telephones were no longer new, though much of the science-based work which led to vastly improved performance still lay in the future.

In 1924 Frank Jewett, Chief Engineer at Western Electric, wrote:"Almost from the day he entered the modest laboratories in Boston, Colpitts took a prominent part in the solution of the problems which were to revolutionise telephonic and telegraphic communication." Colpitts, he continued, was a central figure in the fundamental work which lifted the art of telephone engineering to a higher plane and established it as a science on a firm foundation of exact knowledge.

As well as exact knowledge, exact measurements were now required. The methods and instruments which George A Campbell and Colpitts developed for measuring high-frequency alternating currents were to play a big part in the development of telephony. Colpitts himself "made many of the first high-frequency determinations on lines and apparatus".

In this period up to 1907, under Campbell's direction, Colpitts worked long and hard on the development and application of loading coils to open wire and cable circuits, first suggested by Heaviside but patented by Pupin in 1899. "To those of us who were privileged to witness and occasionally to take part in this work there comes to mind a picture of Colpitts in the early morning hours hard at work in some test room or far afield in sunshine or storm² on a line inspection," wrote Jewett.

Jewett also recorded for us the contribution that Colpitts made to solving, what he called, the threat to the very existence of long distance and even local telephone services in the first few years of this century. That threat was the inductive interference brought about by the introduction of alternating current for the propulsion of trolley buses and trains.

Colpitts threw himself ³ into the work, "sometimes in the laboratory, but now more frequently in rough clothes in the mountains of Pennsylvania or the brush of Georgia⁴ or in rubber boots in the winter mud of Indiana." In the end solutions to the problems were found by joint collaboration with Westing-house power engineers. Jewett credited Colpitts "in large measure" with helping bring about ⁵ the closer understanding between communication and power engineers which came about in the first two decades of the century.

In 1907 the Bell System was reorganised and Colpitts moved to the Western Electric Company (part of Bell) in New York. There he began his climb up the administrative ladder⁶, first as head of the Physical Laboratory, later as Director of the Research Laboratories (1911) and eventually as Assistant Chief Engineer (1917). The technical highlights of that period for Bell were the transcontinental telephone line of 1914, the transatlantic radio telephone experiments of 1915 and of course the introduction of the thermionic valve to experimental and practical engineering. Colpitts was involved with them all.

When he transferred back to AT&T in 1924 as the newly appointed Assistant Vice-President (Development and Research) he was described as possessing a keen analytical ability, the creative imagination of the thoroughly trained physicist, a direct approach, and an integrity of intellect. These personal characteristics received even further career reward in 1934 when Bell's research laboratories merged and he became Vice-President of the Bell Telephone Laboratories.