Paul L. Penfield, Jr. ScD '60

INTERVIEWER: Today is July 26, 2011. I'm Larry Gallagher, and today we are in the MIT Studio speaking with Paul Penfield, as part of the MIT150 Infinite History project. Dr. Penfield was born in Detroit and grew up in Birmingham, Michigan. He attended college at Amherst, majoring in physics and working as the chief engineer on the college radio station before entering MIT in 1955 for graduate work in electrical engineering.

After receiving his doctorate in 1960, Penfield joined the MIT faculty in the Department of Electrical Engineering. From 1989 to 1999, he served as head of the electrical engineering and computer science department, overseeing the creation of the groundbreaking five-year Master of electrical engineering program, and organizing the commemoration of the famous Building 20.

For his work on the commemoration, he received the 1999 Presidential Citation from the Association of Alumni and Alumnae of MIT. Professor Penfield is a fellow of the IEEE, and former chairman of the Boston section. He received the IEEE Centennial Medal in 1984, the Circuits and Systems Society Darlington Prize paper in 1985, and the Circuits and Systems Society Golden Jubilee Award in 1999.

He is author of five books and dozens of articles in his various fields of interest, from electrodynamics of moving media to noise and thermodynamics. Dr. Penfield retired from MIT in June 2005, but still teaches a class for freshman.

Paul, thank you very much for taking the time to talk with us today.

PENFIELD: It's my pleasure to be here, Larry.

INTERVIEWER: So, Paul, your IOP profile states that you retired from MIT in 2005, yet you're still teaching six years later. Why?

PENFIELD: Because I love it. I spent my entire career at MIT. MIT is the kind of place where-- if you retire, you go off and do nothing? That's just not like us professors. Retirement, after all, at any university, especially here at MIT, is really an invention of the payroll office. That is, you don't get paid after you retire. But you can still have all the fun that you had as a professor. And I must say that my years spent here at MIT have been enormously satisfying in a variety of ways. And I've simply had fun. I didn't want to stop.

INTERVIEWER: Great. And you plan on teaching how far into the future?

PENFIELD: Only time will tell.

INTERVIEWER: During your 50-plus years at MIT, you served the Institute in a number of administrative positions. Were you able to continue to teach throughout most of that time?

PENFIELD: I did not. Some administrators-- Paul Gray, perhaps is the dominant example of someone who, while president, actually taught for our department. Other department heads have had a policy of teaching one section of a class, perhaps of a minor nature, but nevertheless keeping their hand in teaching. I discovered that I could not do that. And as a consequence, I devoted full time to administration at that time.

INTERVIEWER: And what is the subject matter, what interests you right now about the course that you're teaching?

PENFIELD: Well, the course that I'm teaching is an attempt to unify two different branches of science. My philosophy, if you like, in doing research is to try to simplify, simplify, simplify, make things easier to understand. And if I find that different branches of science use different terminology for the same concept, why not teach them once instead of twice? Why not allow one field to benefit from the knowledge gained in another field?

And in this particular case, it's information theory, which is a branch of electrical engineering. And it's thermodynamics, especially the second law of thermodynamics, which is a branch of physics and other natural sciences, and is to my way of thinking perhaps the most glorious achievement that science has ever had in its multihundred-year history. And here we have an instance in which the second law of thermodynamics, involving this concept called entropy, is extraordinarily difficult to understand. And some wits have said in the past that everybody who thinks that they understand the second law actually doesn't have a clue about what's going on. And that may very well be true.

However, people nowadays know a lot more about information and how to quantify it and how to deal with it and how to process it. And it turns out that information and entropy really are the same concept, and in suitable structures can be traded one for another just the way mass and energy could be traded one for another. So why teach them twice? Why not teach them together, and teach the differences between the two and simplify things? So that's what I'm trying to do.

INTERVIEWER: Great. And how is it that that course, that subject matter, is well suited toward MIT freshman?

PENFIELD: We developed it specifically for freshmen, and I was alarmed that our curriculum in electrical engineering and computer science no longer requires the students really to have any direct contact with the second law. The second law, as you know, is unlike conservation laws such as the conservation of energy law, which says that there's this quantity called energy which is conserved. And you can transform it, you can move it from one place to another, but at the end of the day, there's still just as much left as there was at the beginning of the day.

Entropy is unlike that, in that entropy of the natural world only increases. It can never decrease, but it generally does not stay the same. It increases. And that's a very mystifying thing. I would say that the natural scientists have never been able really to come to grips as to why that is so, and so on. And yet we humans take it as very natural that we forget things from time to time. We lose information. We never go the other way. Well, information and entropy, being the same concept-- although one's the negative of the other, actually-- so that the natural law which says that entropy increases is the same as the human law which says that the information that you know decreases. It never increases without some kind of interaction going on.

We can take entropy and move it around from one place to another. We can change its form from chemical form to informational form, if you like, in a variety of ways. And at the end of the day, it always increases. If you take a count of all the entropy everywhere in the universe. Now, these two concepts have been developed separately and independently. Claude Shannon, who really invented information theory in 1948, I believe understood that the formula for his concept of information, his quantity, was identical to the formula which was in use in statistical mechanics for entropy. However, he never believed that they were really the same thing, and I don't think it occurred to him to ask or answer the question whether one could be traded for the other in a suitable experiment.

Well, nowadays, with quantum computation going on and as electronic devices get smaller and smaller so you're controlling a larger number of bits with fewer atoms, it becomes important to track the trading of information or entropy, of one form or another, when analyzing the operation of these devices. And it's not crucial yet, but before too many years are out, it's going to be crucial with devices that you can make in standard manufacturing processes.

INTERVIEWER: Might there be an opportunity for this course to become part of the curriculum?

PENFIELD: I think the ideas from this course will become part of the curriculum. I developed the course, and Seth Lloyd has been teaching it with me. He's a professor of mechanical engineering. I developed the course because I wanted the ideas to be tested. I wanted to make sure that they worked. I think the ideas will show up in the curriculum in the future. This course itself probably will not.

But there's another ambition or dream that I have for this course. And that has to do with the fact that electrical engineers and engineers in general-- the concept of engineering and the concept of science is not well understood by our national leaders. Most national leaders are not the result of education in a place like MIT, which is focused on science and engineering and basically prepares somebody for a vocation or employment as an engineer or scientist. They're the results of a liberal arts education.

And by and large, the general education that's given to people who become our national leaders does not have very much engineering in it, and not very much science. So these people are called upon to make national decisions of earth-shaking importance, if you like, without having enough background.

A course such as the one that we developed here, being taught to freshmen, could very well form the foundation of a course which is offered to liberal arts graduates in a general university setting. It would not require heavy mathematics, would not require a lot of prerequisites, and yet they could get the essential ideas. Whatever they do with their life after that, they'd be better informed because of this.

INTERVIEWER: Okay. So it's the importance of taking an engineering-type approach to making decisions, solving some of these challenges?

PENFIELD: Well, the challenges that are faced by our national leadership basically have to do with satisfying, simultaneously, the needs of several different demands placed on them. These people have to be able to make judgments that are based on a wide breadth of information. The trouble is that most people, I would say, don't have the sense of what engineering is, or what science even is. And so they are apt to not be able to make those judgments very well.

And just a couple of courses could help, one on a conserved quantity, like energy, and one on a non-conserved quantity, like information. And those two could provide metaphors which the people could use throughout their careers in understanding what scientists are saying, understanding what non-scientists are misunderstanding about what they're learning, etc.

INTERVIEWER: So what are the challenges with introducing those kinds of courses into a liberal arts curriculum at schools throughout the country?

PENFIELD: Well, MIT does not have a liberal arts curriculum, so I'm really not much of an expert in this. I would like very much to see some universities-- Harvard is a perfect example of a university that could do something like this if they wanted to. So far they haven't seen examples of it done, and I think our course may provide an example they can look at. A course on a conserved quantity-- I'm not sure that there is an example that I know of. Probably there is, but I'm just not aware of it. I think the difficulty is that it has to be done locally by somebody in the university who passionately cares about doing it. And I'm not that person.

INTERVIEWER: Right. But from what you've outlined, there could be opportunities up the street at Harvard?

PENFIELD: There could. And if Harvard didn't want to do it, there are probably dozens of other places that could do it.

INTERVIEWER: Let's go back to the beginning. We were just talking about what you've been doing recently. I want to go back to the beginning of your education. Can you please tell me a little bit about your family and growing up in Birmingham, Michigan?

PENFIELD: Well, I was your typical geek at the time, or nerd. Those terms weren't used at the time, but they certainly seem appropriate now. At the age of 10, I was interested in making crystal sets rather than playing baseball. And I think many people at MIT share that same kind of a background. We were the consummate nerds.

INTERVIEWER: Were there others in your family, or your parents, that instilled this interest in you? Is this something that you just did on your own?

PENFIELD: Yeah, I just did it on my own.

INTERVIEWER: You were building more than your typical Heathkit. You were actually building pretty sophisticated Heathkits.

PENFIELD: Well, I did. The Heathkit, as you know, was a product line put out by the Heath Company of Benton Harbor, Michigan, right after World War II. They got all this war surplus gear, and that's how they made their living for a while. But then they realized that they were going to run out of this stuff, because the army only had bought so much that was surplus. And so they cast around for a market, and they decided to make kits where they would supply the electronic parts and complete instructions. And their success depended on having a good set of instructions which you could easily follow.

And you could make multimeters, you could make amplifiers, you could make oscilloscopes, you could make all the kinds of test equipment that was pertinent at that time. And these were all vacuum tube-type things. Transistors hadn't been invented at that time. But I made a bunch of them. I was 10, 11 years old during the war, and I was making crystal sets at that time, along with a few friends who were geeks like me.

INTERVIEWER: Was there a particular "ah ha" moment, growing up, when you realized that you had a special aptitude for doing this?

PENFIELD: I'm not sure that there was. I just always knew that I was more interested in this. And when I did playacting and that sort of thing, I playacted by setting up a radio station studio, rather than by kicking a football.

INTERVIEWER: Was there a particular teacher that inspired or motivated you to pursue this interest.

PENFIELD: I don't believe so. I don't believe so. I have no idea where it came from, but I was just interested in science. I listened to the radio and I thought radio was kind of neat. There was no television at that time, of course.

INTERVIEWER: I also read you had a keen interest in genealogy, and you can trace your family back to 1651. And Samuel Penfield was the first Penfield born in North America?

PENFIELD: Well, to the best of our understanding.

INTERVIEWER: Are you the person in your family most responsible for tracing your family's roots?

PENFIELD: No, I'm not. There are people who did that well before me. And I happen to maintain the website in which the Penfield genealogy is available online. Previously, it's been available in book form. And of course, being available online means you can make corrections and additions all the time. And I have fun doing that.

INTERVIEWER: I recall listening, I think it was just yesterday, to a keynote that you delivered at Kresge Auditorium as part of the EECS 100th Anniversary. And in it, you cited a Penfield that was responsible for some development of some early technology. Was that Penfield a descendant?

PENFIELD: That was a Penfield. He isn't my ancestor.

INTERVIEWER: Yeah, ancestor, that's what I meant. OK. It was not your ancestor.

PENFIELD: That was not one of mine. That was Allen Penfield, who owned an iron mine in Crown Point, New York. And he purchased electromagnets from Joseph Henry. And Joseph Henry was the dominant scientist in the US at that time. During the 1830s he was located in Albany, and he made electromagnets and he did scientific experiments with them. And it was very cumbersome to do such things, because there weren't batteries available at that time.

Penfield bought a couple of these things and used them to magnetize spikes on a drum which separated iron from iron ore in his iron mine. And he got increased yield because of the increased efficiency of the separation due to the magnetism. And he kept these spikes in his drum magnetized by using an electromagnet that he purchased from Henry. So that was said to be the first industrial use of electricity in the nation. And there is now a museum in Crown Point, New York. The Penfield homestead has been made into a museum which celebrates that achievement.

INTERVIEWER: So you clearly have a great interest in the history of technology.

PENFIELD: Well, it's fun. It's fun, and there are fascinating stories from history. And I think I have an appreciation that history forms a context in which you can understand the present and the vector in which you are moving toward the future. And without the knowledge of the history, you pretty much can't chart your own course.

INTERVIEWER: Certainly. Certainly. So let's talk about the evolution or the invention of the transistor, and how that impacted your life.

PENFIELD: I did not invent the transistor.

INTERVIEWER: You did not invent it. But it certainly transformed or it was a keen interest of yours, even back as a young boy.

PENFIELD: Well, I was 14 years old when it was invented in 1947 at Bell Laboratories. It was a celebrated achievement. Bell Labs had been looking for a solid state device that could replace the vacuum tube, which was notoriously inefficient in its operation. It worked very well for some purposes, but it was very inefficient in terms of power, and costly, and so on. And they were looking for something made out of solid material that could do it. And they knew that you could make rectifiers out of solid materials, the so-called point contact rectifier, the cat's-whisker, and then the galena samples that were used in crystal sets.

As a kid, 10 years old, I was making crystal sets. I knew how to do that. I knew how to wire up the telephones. I wired our home telephone so that I could have an extension in my room. And the telephone repairman came around and fixed my mistakes and left me a note and told me what I did wrong. Then a couple of years later, I used to hang out with the telephone repairmen in the congregating place in the town where I lived. And they'd teach me the techniques that they used and how they strung wire and all that sort of stuff. And I was just fascinated by that.

INTERVIEWER: I understand that you were a bit skeptical about the first generation of transistors, due to I guess their fragility?

PENFIELD: Well, I was 14 years old at the time-- 13, something like that. The transistor was announced, and I had spent time making crystal radios, and I knew how difficult it was to find the exact sensitive spot on the crystal where you could do it. And these people made a transistor by having two cat's-whiskers that were close to each other, and both of them had to be in exactly the right location, not too far apart but not too close either. And I just knew that that was too fragile to be commercially possible. Furthermore, I confidently a lot of my friends, my geeky friends who would care about something like that, that I was sure that this would not amount to anything since the devices had no filament, and everybody knows that vacuum tubes had filaments. Of course, that was the whole point.

INTERVIEWER: So how would you describe William Shockley's contributions to transistor technology?

PENFIELD: Oh, well, he was the father of all that kind of stuff. He headed up the whole group at Bell Labs that developed it in the first place. And he personally invented the junction transistor, not the point-contact transistor, which was the early one. But three years later, he came up with the theory of the junction transistor in a glorious paper in 1952. He laid it all out and made it actually believable. And Bell Labs started making some of them. Companies started making some of them. The first application of transistors that were really reliable like that-- and those were the first ones that were--

INTERVIEWER: Reliable. That was the biggie.

PENFIELD: --reliable and manufacturable. The first applications were to hearing aids. And Raytheon, here in Massachusetts, was one of the companies which wanted to get into this business. And they made transistors specifically for hearing aids. Now, most of the transistors then didn't work very well, and so they were the rejects. And so here they have maybe five or six transistors that work well that they could make hearing aids out of, and 50 or 100 transistors that didn't meet specs. What are they going to do with them? Very cleverly, they relabeled them and made them available to people who were hobbyists, who could then develop circuits of low quality, but nevertheless innovative circuits, making use of them. And they gave them away, or they sold them very cheap. You could actually buy transistors very cheap. These were rejects from the--

INTERVIEWER: Did you get access to any of those? Did you get one?

PENFIELD: Anybody could buy them. You could buy them at Allied Radio Company in New York, or Lafayette. Or Allied was in Chicago, I guess. Lafayette was in New York. You could buy transistors from there, and if you understood how a vacuum tube worked and you understood how a transistor worked, you could actually make circuits.

INTERVIEWER: So when did you start actually building things with transistors?

PENFIELD: In the early 1950s. It was fun. I had built some stuff with vacuum tubes before. I figured it would be fun to try transistors. I burned out some by soldering them too close to the body, and made all the usual mistakes that people made at that time. But I actually got some circuits to work, and I had a lot of fun doing that.

INTERVIEWER: So how did, then, you decide to go to Amherst for your undergrad education?

PENFIELD: I basically didn't think about it. I just followed advice that was given to me. My grandmother thought that I ought to go to MIT, but she didn't know anything about it. My parents thought that I should probably have a liberal arts background, and so they pushed Amherst as well as some other places. And I eventually got accepted at some places, the same as happens today. And I made the choice on not very good grounds, but I think it was a good choice anyway.

INTERVIEWER: Did you go to Amherst with the intent of following-- at the time, there was a 3-2 program at MIT?

PENFIELD: Yes, I was.

INTERVIEWER: Can you talk about that a little bit?

PENFIELD: Yes. The so-called 3-2 program, which existed at that time, was between MIT-- other technical universities might have done it also, I'm not sure, but certainly MIT did, in concert with half a dozen or more of the small liberal arts colleges. And the idea is that you can go three years to the liberal arts college, then come to MIT, go two years, and get two Bachelor's degrees at the end of the five years, one from your first institution and the second one from MIT. Amherst had that arrangement with MIT. Williams did. A variety of other schools did as well.

And I thought it was a wonderful idea. However, by the time the three years were up, I thought, I'm having so much fun here, I'm just going to make it a 4-1 instead of a 3-2. It didn't work out quite that way. It was four, one and a half or four, two, or something like that. But it didn't matter, because I got into MIT. The reason I got in was that I had been intending to come as a 3-2 person, so I was not unknown to MIT. And that, I think, helped my admission.

After I got here, I had to enroll as an undergraduate because I lacked the engineering background. I found it relatively easy, because my physics background and my math were fine. I got those at Amherst, so I was able to go fairly rapidly through the undergraduate requirements. When I did that, and I satisfied all the degree requirements, the said, oh, you don't need a degree. Why don't you join the doctoral program? So I did. The rest is history.

INTERVIEWER: That sounds like such an intriguing program, and one that would probably be popular today. But I have to think that if somebody were to spend three years at a liberal arts college-- if that program existed today, and they were to spend three years somewhere else and come here for two, it would seem, knowing what I know about the current undergraduate curriculum, that it would be difficult for those 3-2 students to get the same level of technical education that a four-year MIT undergraduate would get.

PENFIELD: I don't think so. I don't think so. They can pick up the mathematics and the basic sciences which are taught at many different small undergraduate colleges. Wellesley is an example of a college which could do this very naturally. They teach science very well, perhaps not engineering. And then they come to MIT. I don't see any reason why it couldn't work today.

INTERVIEWER: What became of the 3-2 program?

PENFIELD: It was abandoned. I don't think it was too popular. If it had been popular, they would have figured out ways to make it continue, I'm sure. But I don't personally know. I lost sight of it.

INTERVIEWER: So, going back to Amherst, how did your involvement in the college radio station add to your education?

PENFIELD: We did a lot of activities, of course. And I joined the radio station because I was interested in audio and in electronics and circuits and all that kind of stuff. And I was the only geek there, so I had full reign to do whatever I wanted to and nobody could argue with me. If I wanted to change the microphones around, I could do that, and they would just go along with it. And that worked out well. It gave me some practical experience. Then it also gave me an interesting project that turned into my first publication, as it turned out.

One of the things that we wanted to do from time to time was a remote pickup. And a remote pickup-- if you're going to a different city, you call the telephone company and say, I want a radio loop between here and there. And Larry, you probably know what a radio loop is. You attach your little remote amplifier at the far end, and you have a direct loop back to the station and they can put you on the air from wherever you are. We did remote sports broadcasts that way.

We wanted to do something similar when there were events on campus, either lectures or concerts or recitals or sometimes just plain incidents that happened, bonfires and rallies and that sort of thing. We wanted people to be able to walk around and make broadcasts. Previously, what we had done is take along a tape recorder, which at the time were rather large and you had to strap it onto your back to carry it around, unlike today's tape recorders. And then you had a microphone and the reporter, the talent, would talk into the microphone. And then you'd run back to the station and play it. It wasn't done in real time. And we wanted to do it in real time.

One of the things that we did was wire up the campus. We climbed through all the steam tunnels. We hacked into the lock systems. We made our own keys just the way MIT people did at that time, so that we could get into all the buildings and not have to call the campus patrol to let us in. And we ran wires from our building to all the other buildings on campus. Then I decided what we needed was a portable remote amplifier. And the purpose of a remote amplifier is to amplify a microphone signal up to a few volts to transmit back to the station. If you try to transmit the microphonic signal directly to the station over a set of wires, there's too much noise. It doesn't work. You have to amplify it first. That's true today as well as it was 50 years ago.

Well, 50 years ago, the only way of doing that was vacuum tubes. But hey, the transistor had just been invented. And this was the early 1950s and Raytheon was making these transistors, the CK721 and the CK727, the CK722, depending on whether they were low-noise or regular-noise or more rugged, and so forth. They had this line of rejects from their production of hearing aid transistors. And they were relatively cheap. So I designed this little remote amplifier. And it was nice. The only thing is there weren't any power transistors at the time. So the only thing I could do is do the preamplification-- I had to follow that by a tube which could put out enough power. So you have to have the battery to run the tube and a little tiny battery to run the four transistors that were in there.

Well, I could see where this was going, but I decided to build it with what I could do at the time. And in the summer of-- I think it was 1953, I was at home and I just built up this little remote amplifier. As I recall, it had two microphone inputs, so the interviewer and the interviewee could each have their own microphones. And then in the fall of 1953, I brought back to Amherst to the radio station.

And the engineer would strap it on his back. And it was fairly lightweight. It could be done. We'd run a pair of wires down to the nearest the point, using alligator clips to clip onto the radio loops that we'd put all over campus. And he could do a real-time broadcast from anywhere on campus that we could run a pair of wires. And that was an innovation. It hadn't been done before.

INTERVIEWER: Well, yes, it was one of the first applications of transistor technology for audio transmission, wasn't it?

PENFIELD: I believe it was. There were obviously a lot of companies that were working on this, trying to do it. And the company having to do it, of course, had to make something which was rugged, was much more reliable, and was able to be sold at a profit, and so on.

INTERVIEWER: But meanwhile, as an undergraduate student at Amherst College who's building this, and you're doing it at the same time companies are developing this?

PENFIELD: That's right.

INTERVIEWER: You're originating these remote broadcasts in Amherst with stuff that you put together yourselves?

PENFIELD: That's right. That's right. It's something that I put together myself. And I didn't have to have the quality of robustness that a commercial product would have to have. So I was able to do it without, necessarily, the intense engineering which should have been done at that time.

INTERVIEWER: Did others in the Amherst student body-- were they aware that there was this kind of cutting-edge application of this technology going on on campus? Or did they just accept it?

PENFIELD: No, they said, "oh, that's neat. Now we can talk and not have the delay getting the tape back." So they thought it was neat. And they figured out how to make use of it in their broadcasts. And we had a student riot at one time, as happens at many colleges of course. And I forget what the incident was. But here's the engineer out there in the middle of it, trying to make sure that the wire which led back to the nearest building didn't get trampled on, and the announcer interviewing people right on the spot. And it was going on over the air as he was doing the interview. This was something that I don't think had been done before at Amherst. It was a lot of fun.

INTERVIEWER: And there was an article written about it. Did you write the article? Or was somebody else documenting that this took place?

PENFIELD: I wrote the article. I decided that this was an interesting application. I hadn't seen any article about this, and I didn't know anyone who'd done it. So I wrote it up and I sent it in to Audio Engineering Magazine. Next thing I knew, they published it. And I was surprised. And they shortly thereafter sent me a check. They paid $28 a page. Or was it $30? I'm not sure. And this occupied about three pages, and so I got a certain amount of money from this. And at that time, that was very welcome.

INTERVIEWER: So then that led to-- because I know that you went on to write quite a bit in graduate school, which we're going to talk about, but what I want to do is to get you to MIT. So how did you decide-- did you know already that you were going to be going to MIT after Amherst? Did you know before you went to Amherst that that was the next step?

PENFIELD: Oh, yeah. I also applied to the University of Michigan because I thought they had, and I know that they have, a good engineering school. And they still do. I would have been happy at the University of Michigan also, I think. But MIT was closer to Amherst. University of Michigan was closer to home. MIT accepted me and so I went.

INTERVIEWER: So let's do go to, then, your prolific writing career while a graduate student at MIT. Tell me about how all that developed.

PENFIELD: I don't know that it was prolific at all. But I did, after successfully writing this article and getting paid for it, I thought, this is pretty neat. Maybe I can do some other things. And I had some other ideas for projects that I could do. While I was still at Amherst, I developed beach phonograph amplifier. And the way that worked is that there were these windup turntables for 78 RPM records. And the windup turntable used to have an acoustic arm, and then the acoustic arm would play it. And there would be no electronics.

So I substituted for that a regular crystal which was used in other audio gear at the time, but still the windup motor, and then later a transistor amplifier and speaker and that was neat. It worked. And I took a photograph of a couple of my friends on the beach with it. And not only was the article published but they used the picture on the cover of the magazine. So I got a little extra money for that.

Then I did other projects. I made a headlight dimmer for automobiles, which is based on a kind of optics with an astigmatic lens, and a transistor so that you could see lights coming on the horizon but not coming too high or too low. And so it differentiated between streetlights and oncoming traffic, and it would automatically dim your lights when a car was coming. It worked, but I'm not sure it was practical. I wrote it up and published it, and got paid for it also.

I made some other things, a guitar amplifier and various-- there were a lot of projects. During a certain period of time from 1954 up until I got my doctorate, I wrote several articles about transistors, some of them about construction projects which I had done. I loved to do the construction projects, design them and carry them out and photograph them and document them and sell the articles. And some of them were how-to articles about care of transistors. Some of them were the theory behind transistors.

It turns out that transistors had just come into the public view. Not many people who were hobbyists in electronics knew about transistors. And I did because I studied them. It was a fortunate coincidence that I was the right person at the right time, if you like. And I knew that. So I would sit down while I was a graduate student at MIT-- as an undergraduate and graduate student, as I explained. I had one and a half years as an undergraduate.

During that five-year period that I was at MIT before I got my doctorate degree, I actually sat down in the evenings and on weekends and I'd grind out one article after another after another. And I could do them fairly prolifically.

INTERVIEWER: Well, that's why I used the word. Because you did. You had quite a bit of-- in fact, I read where the income from some of this writing actually one semester paid your tuition.

PENFIELD: Oh, yeah. Tuition wasn't very much then. It was only $500 a semester. But rather than have an assistantship, I figured I could make more money writing. And I think maybe I did. My wife had a job, so I didn't need to worry about eating. And I simply wrote one article after another after another and made enough to pay the tuition. I joke and say that I put myself through graduate school writing articles. Now that's a stretch, to be sure, but it actually happened one semester.

INTERVIEWER: So tell me about your first impressions of MIT, particularly compared to your experiences at Amherst.

PENFIELD: My first impressions of MIT were that this was a really geeky place. At Amherst, I'd been the only geek in town, in a certain manner of speaking. But here, everywhere I went, there was another one like me. And it was great to see these people.

INTERVIEWER: You felt you belonged, right from the get-go.

PENFIELD: Yeah. Well, I felt I belonged at Amherst, also. I never had a sense of not belonging. But I knew I was different from most of the people there, who have gone on to very fine and illustrious careers, but they weren't interested in engineering. And I was.

INTERVIEWER: So you must have had so many great relationships with faculty as a graduate student, given the fact that you were so eager to test things, try new things, roll up your sleeves, build things. What what was the graduate years like?

PENFIELD: Well, it was a lot of fun being a graduate student here. I guess three or three and a half of those years I was actually a graduate student. In the first year and a half I was still doing undergraduate. So as an undergraduate I had great fun understanding how the physics that I had learned actually applied. You could do quantitative things with it. You could actually solve for field configurations. I knew that fields existed, but I haven't known how to actually calculate them in any sense. I didn't have any judgment about what they were. This is the difference between science and engineering. And I picked that up. That was fun.

Then, watching the engineering faculty and the fun that they had--

INTERVIEWER: What were some of the more interesting faculty that you worked with?

PENFIELD: Well, I didn't work with Doc Edgerton, but of course everybody knew him. And he was a lot of fun. We had annual Steak Frys in Course 6. And he would come down with his guitar and play. And I used to play guitar, and he was much better than I was, but he invited me up anyway, and we made fools of ourselves. And we had a lot of fun.

I worked with Hermann Haus on my thesis. And the way that that turned out is that I was in charge of the rotating machine lab one year. Rotating machines were on the way out as far as the education here goes. And I sort of knew that. Westinghouse had made what was called the generalized machine, and they had modeled certain parts of it, but we didn't have a model which was inclusive. And I suddenly realized that this was true, and I looked around, and I didn't see anyone else doing it. So I went home one night and developed the general model, all the equations necessary for the general model. It was too complicated to use for very much, but there it was. And I made it available to all the others.

I was put in charge of that, and then I was also interested in the IEEE, the Institute-- well, it was the Institute of Radio Engineers at that time. They put on a series of lectures by eminent people. And one of the people gave a talk about masers, which had just come out. These were the predecessors to lasers, which are so common today, but at a lower frequency. And they mentioned some conservation laws that had been developed for masers. They were known as the so-called Manley-Rowe equations. And I looked at them and I figured, gee, they also ought to apply to rotating machines, not just to the kind of devices that were used that these physicists.

And so I figured out, well, gee, maybe I can make some of the circuits that they had made, but on a much lower frequency scale-- not for any practical purpose, but just to see whether they'd work. One day I was in charge of the laboratory using this generalized machine, and all the students were doing their stuff. And I had nothing to do, so I grabbed one of the other students, and the two of us together sat down and I explained what I wanted to do. And then he said, yeah, I think this ought to work. We sat down, took an hour, and got it to work.

That other student turned out to have an illustrious career. That was Al Oppenheim of our department, who had quite a career here at MIT and is still on the faculty. He used to say later that he wrote his first technical paper with me when the two of us wrote that up as a technical paper.

INTERVIEWER: I would imagine, given your skills at both writing and building things and experimenting, that you were on a fairly fast tenure track.

PENFIELD: I think so. I got the doctorate three and a half years after becoming a graduate student.

INTERVIEWER: And then how long after that did you become tenured faculty?

PENFIELD: I just rose through the ranks. At that time, the department was expanding, in part because the Ford Foundation was in trouble with the IRS. They had to give away a lot of their money or they were in jeopardy of losing their tax exempt status. So they gave a lot of it to MIT and established Ford postdoctoral fellowships that were available to hire new faculty. Well, I was one of those.

Many of those people were told explicitly, you have a one-year, or two-year, or three-year, as the case may be, appointment and that's it. And I heard them grumbling among themselves, and then I realized, I hadn't been told that. I was one of these also, but nobody had told me that. And I started to worry that maybe they weren't telling me something, but the fact is they weren't telling me something for a good reason. And I stayed and the others did have only temporary ones.

But I joined the faculty and rose through the ranks at the normal rate.

INTERVIEWER: So I want to talk a little bit about change. You came to MIT in 1955, over 55 years ago. I'd like to explore some of the changes and transitions you've experienced during that time. So let's start with technology. And you're talking to a fairly non-technical person here.

PENFIELD: I'm not talking to you anyway. I'm talking to the audience who's out there in Never-Never Land.

INTERVIEWER: Exactly. Exactly. But you have stated that many of the developments in your field at MIT since 1950 have to do with semiconductors in one form or another, because that technology became so pervasive and dominant.

PENFIELD: That is true.

INTERVIEWER: First as transistors, then as integrated circuits, then as VLSI, and now as system integration. Can you talk about the impact of these developments, and in particular, the practical applications of these technologies?

PENFIELD: Well, I think the practical applications of these technologies has been to take over all the electronics and the information handling. And I think it's pretty well-known and pretty well-accepted that all of the stuff that you buy nowadays, the electronic gear that you buy, is all based on transistors. And there are more transistors in a car today than were ever manufactured before 1960, every single car. Airplanes nowadays are nothing more than crates that carry around 50 million lines of code on computers that run them. Everything that's made today relies on transistors, and on semiconductors.

And the way in which that happened, though, did involve a transition between what is now known as analog electronics and digital electronics. And this actually took place-- there were the precursors of this in the late 1950s, even. There were some precursors to this. But it happened in earnest after the development of the integrated circuit in 1960, where you could stuff more and more transistors on a very reliable surface and have them permanently connected together, and not have to worry about wiring them up and soldering them and all this kind of stuff.

And the digital abstraction and the encoding of normal information into digital form really took off during the 1960s. And it became a dominant new form for electronic engineers, who up to that time had not had to worry about computers. They'd never seen a computer of course by that time. And they didn't know anything about it. But suddenly they're confronted with having to work with digital signals rather than what are now known as analog signals. And they had to relearn a lot of what they know.

So that transition which happened in electronics actually was very significant to our department, because that helped inform a lot of the developments that went on in the our department at that period of time.

INTERVIEWER: So you came here as a 22-year-old student. What aspects of the MIT culture and the MIT student body have remained constant during that time? And what are the most significant changes that you have witnessed during that time?

PENFIELD: Well, certainly the fact that MIT appeals to geeks was true then, although the word wasn't used at that time, and it's true today, and I suppose it will be true into the future, no question about it. What you're a geek about has changed. One thing that has changed I feel is an unfortunate development, that it's not possible for people with my kind of experience, my kind of hacking experience, to come here anymore.

Now let me explain what I mean by that. When I was 10 years old, I was making crystal sets, as my fellow geeks all over the country were at that time. In what is now called middle school, I learned about the transistor and I started making transistor circuits as audio amplifiers and so on. And we've gone through some of that. Nowadays, there's no challenge to that. People can make crystal radios but it's just not the same. You don't have the same thrill.

When I was young, I took apart an automobile engine. I learned how to use hand tools in doing that, and I really screwed it up and lost the car, but I only lost $75 so it didn't matter all that much. Nowadays, if you look underneath the hood of your car, you'll understand why nobody can ever service their own car anymore. It's just now all specialized. And if you take apart any electronic gear, you'll find that it's all encased integrated circuits. You can't really do the kind of things which give you a hands-on experience, at least in most domains.

Nowadays, the hands-on experience that students have when they come in is more of a keyboard. And so it's one step removed from reality. And that's unfortunate, because if you're going to teach people concepts as we want to at MIT, the best way of doing it is to have them have concrete examples of that. And then you teach the abstractions which tie together all the various concrete examples that you had. And then you can remember the abstractions and work with them in the future.

INTERVIEWER: But you've just pointed out though-- but where are the opportunities to do that? Do we have to manufacture them?