In Memory of Professor Sidney Darlington

Dr. Sidney Darlington, an Adjunct Professor in our department passed away at his home in Exeter, NH, on October 31, 1997, at the age of 91. Dr. Darlington was one of the world's most creative and influential circuit theorists. Every electrical engineer knows of the Darlington transistor configuration. He made significant contributions in several areas including network synthesis, radar systems, rocket guidance, and transistor networks.

Dr. Darlington was born in Pittsburgh, PA. He received the B.S. degree in physics (magna cum laude) from Harvard College in 1926, the B.S. in electrical communication from MIT in 1929, and the Ph.D. degree in physics from Columbia University in 1940. In 1929 he joined the Technical Staff at Bell Laboratories where is worked until he retired at age 65, as Head of the Circuits and Control Department. He received the Presidential Medal of Freedom, the highest civilian honor of the US, in 1945 for his contributions during World War II. In 1975 he received the IEEE Edison Medal and in 1981 he received the IEEE Medal of Honor.

When Dr. Darlington was more active he loved to tinker with things, whether mechanical devices, calculators, computers, or equations. He took pride in removing big trees at his camp in Randolph, NH that needed to come down. He used a come-a-long and great care and calculations to drop the trees so as to miss the house, power lines, etc. He loved to use mechanical advantage in his projects.

He was intrigued with the way things worked. When he was going over to Manchester, NH to get radiation treatment for prostate cancer in the early 1980's he would talk with the radiologists about the x-ray machine. Our guess is that he knew more about the machine than either the technician or radiologist. He would make mental estimates of energy, accuracy of aim, etc.

He was a lifelong hiker and AMC member. He and his family hiked in the Presidential Range and elsewhere on their stays in Randolph. Dr. Darlington was quite proud of the fact that he climbed Mt. Washington on his eightieth birthday. He was especially interested in the ways of nature, and he had an inquisitive eye in looking at natural phenomena. He also liked to canoe. He and his wife Joan spent their honeymoon in the Boundary Waters Canoe Area Wilderness of Minnesota.

In his earlier days Dr. Darlington was a great storyteller. He had stories about the Pacific during World War II, about people he has known, about almost anything. His discussions and stories often revolved around former well-known Bell Labs colleagues such as Shannon, Bode, Norton, etc. The reference to the Darlington pair transistor was the subject of one of Dr. Darlington's stories. Just after the transistor was invented at Bell Labs, he checked out for the weekend two of the few existing transistors from the head of Bell Labs. Transistors were not generally available and the head of the Labs kept the few that had been made in his desk. He played with them at home on the weekend and discovered/invented the Darlington pair. He realized that they could be put in one package ("On one chip"), and that in fact any number of transistors could be put in one package. The next week he was encouraged to have the lawyers draw up the patent application. He said it should be written for any number in one package, but the lawyers only wanted to do it for two, and applied for the more restrictive patent. As it turned out, if it had not been restricted to two transistors, Bell Labs and Dr. Darlington would receive a royalty on every IC chip made today! Anyway, that's the story he told.

After his retirement in the early 70's from Bell Laboratories Dr. Darlington became an Adjunct Professor in the Department of Electrical and Computer Engineering at the University of New Hampshire. He received an honorary doctorate degree from UNH. When Dr. Darlington joined the faculty at UNH he and his wife Joan had a young daughter, Ellen, and a second infant daughter, Becky. Ellen, who now is living in England, has done work in radio and in the technical aspects of theater and is currently applying her "handi(wo)man" talents to fixing up a boat. Becky is working on an advanced degree in physics at UC Davis and working at Livermore Labs in California. Dr. Darlington taught several graduate courses in digital and analog filter theory for a number of years at UNH, and he talked to undergraduates about some of the ideas with which he had been associated.

The Chirp technique originated at Bell Labs in a proposal made by S. Darlington (1947) in connection with waveguide transmission. The designation "Chirp" was first used by B. M. Oliver in a 1951 Bell Laboratories memorandum entitled "Not with a Bang, but a Chirp. It was recognized as a way of satisfying the requirements of pulsed radar systems in providing long-range performance and high range resolution while avoiding the problems associated with generating and transmitting high peak powers. This concept involves (1) transmitting a relatively long pulse, modulated in frequency over a bandwidth appropriate to the desired range resolution, and (2) collapsing this long pulse, on reception, into a short pulse by means of a network which selectively delays the signal associated with the various transmitted frequencies. The earliest Chirp systems used dispersive networks of distributed or lumped electrical components, and a large body of knowledge in the field of network synthesis has evolved from the development of these networks. Starting about 1957, acoustic Chirp devices were developed at Bell Labs which depended on the dispersive propagation in acoustic transmission media such as fused quartz, steel, and aluminum. The Chirp concept has stimulated the development of many circuits, Chirp subsystems, complete radars, and special devices to implement the Chirp principle not only at Bell Laboratories but also in other companies and universities in the United States and abroad.

The Bell Laboratories Command Guidance System guides the rockets that have launched most of the free world's unmanned scientific space vehicles. Dr. Darlington, of the Mathematics Research Department at Bell Laboratories, conceived the original principles in 1954. He combined the radar tracking technology, based on a system invented by J. W. Schaefer and E. L. Norton and developed by Bell Labs for Nike Ajax and Hercules, with basic inertial properties to evolve a precise but simple radio-inertial guidance system. Particular advantages were the reliability and relatively low cost of the missile-borne equipment expended on each firing and the flexibility of trajectory selection inherent in the ground-based digital computer. Originally developed by Bell Laboratories for the U. S. Air Force Titan I intercontinental missile, the Bell Labs command guidance system was adopted in 1959 by NASA for guiding its space vehicle boosters such as Thor Delta. Echo, Tiros, Transit, Telstar®, relay, Syncom, Pioneer, Essa, Nimbus, Bios, and Intelsat are some of the familiar names of satellites launched with this system. Guidance stations are operated by the Western Electric Company at both Kennedy Space Center in Florida and Vandenberg Air Force Base in California. In over 300 launchings in nine years, the system had no failures of missile-borne guidance equipment and only five failures ascribed to ground equipment or human errors.

In the November 25, 1961 Business/Financial section of the New York Times there was an article entitled "SYSTEM PATENTED TO GUIDE ROCKETS" with a picture under the heading "Mathematician Develops Rocket Guidance System. The article reads:

Washington, Nov. 24- A mathematician has patented for Bell Telephone Laboratories, Inc., New York, important principles of a rocket guidance system that has already operated without a failure in more than sixty firings. This week it directed an Air Force Titan I missile 5,000 miles down the Atlantic missile range. Dr. Sidney Darlington, the inventor, successfully combined two systems that had been used separately- radar tracking from the ground and "inertial" control by instruments in the rocket itself. Information from both sources is fed to a computer and forms the basis of control by radio. The Bell Laboratories command guidance system has directed thirteen satellites successfully into orbit, besides aiming intercontinental ballistic missiles with accuracy. The system guided a two-in-one launching last week. This put into orbit the Transit IV-B navigational satellite and the TRAAC (Transit Research and Attitude Control) satellite that is testing the feasibility of using the earth's gravitational attraction to orient and stabilize a vehicle in space. Previously it had guided into orbit the Echo I communications satellite, three Tiros weather satellites, two Explorers and five Discoverers. Before a ballistic missile is fired, a trajectory is determined to achieve the launching of a satellite or to strike a distant target. Guidance is applied only until the rocket engines are shut off. After that the missile flies like a bullet that has left a gun barrel. With the patented system, radar tracking on the ground determines the position of the missile, and other instruments, usually in the rocket, show its velocity. Dr. Darlington developed a formula for weighing information from both sources, and for "Smoothing out" the radar data. The computer gives the necessary steering commands to an automatic pilot in the missile. Dr. Darlington, who has been engaged in applied mathematics at the Bell Laboratories for thirty-two years, expressed his solution in the patent (No. 3,008,668) as a complex mathematical formula. As he is also an engineer, his twenty-four patents cover inventions in other fields, including a transistor circuit that is widely known by his name. He is a senior member of the American Rocket Society.

Dr. Darlington's mathematical, engineering, and inventive skills have influenced many individuals, universities, agencies, and corporations. We are grateful that Dr. Darlington was part of our faculty.