PPT/ODP/PDF vs White/Blackboard

Following up on a facebook post and adding some more references and links as well as a poll for the fun of it . Also  noticing that there are 10 months since I posted here … other types of media have been used.

So, the question was about what we prefer to listen to. What type of performance do we prefer in the lecture hall – powerpoint or whiteboard? Personally, I do not feel very comfortable using powerpoint [PDF/ODP/beamer/whatever] to present nor listen to. The lectures I mostly enjoy are either the ones with just a few “simple” slides, or simpler annotations. For example

or why not the great lectures by

where you can find lectures by Prof. Adams or why not the great lectures by

(Yes, I admit that this is a “meta-discussion” in the sense that we watch someone lecture on a youtube channel thus making it more or less a powerpoint presentation – but I think you know what I mean).

I would also like to highlight the

that display a method that is somewhat in-between. A static “slide” (landscape?) but a detailed walk-through of the stuff on the board. Some of his “wild” [pun intended] ideas aside, it is comfortable to listen to him.

Back to powerpoint (or PDF or ODP) [copy from the facebook pages]: What especially annoys me are those presenters who read out loud the text displayed on the screen. The audience has already read the whole page twice before the presenter reaches the end of first sentence. And mostly, they have already understood the contents before presenter starts to mumble and desperately tries to remember what they’ve written three years earlier.

Too many times I have had lectures where the students have fallen asleep – more or less. It does not really matter if I distribute material in advance.  Yes, I know it is also my fault – I should probably prepare better slides and present them better. Perhaps I make the errors mentioned above.

But taking the pen and massaging the text and moving across the whiteboard is more satisfying. Making some errors now and then and erasing and rewriting after interaction from and with the audicence makes the presentation more live.

The downside is of course efficiency – which is important! – there is limited time slot in the teacher’s schedule and in the students’ schedules. Watching a professor slowly writing the formulae on the board could sometimes be as interesting as watching paint dry.

The combination of slides and board? Well, there is a risk of interupting the flow. There is no natural way of conetext-switching. Displaying some complex graphs? Equations? Well, yes, perhaps – but reproducing them line-by-line on the board is also part of the explanation procedure.

I am thinking of this graph, where yellow displays the “match” between entertainment and learning level. Doing the repetitive stuff, over and over again, is perhaps not that fun, but learning is better IMO. Think of it as a movie with Schwarzenegger vs a documentary with Attenborough vs peeling 200 kg of potatoe. (Well…) There are differences between being entertained, interacting and just performing repetitive patterns.  Can we fill the white boxes with yellow knowledge?





MM-48-130-10, case file 38139-8

[Nerd alert!] Comments to memorandum MM-48-130-10, case file 38139-8, från BTL

Quite a while now I’ve been fascinated by Bell Labs (Bell Telephone Laboratories, BTL). The famous lab that had its best days around and between the world wars. Nowadays Bell Labs is “owned” by Nokia, and hopefully the good traditions are carried further.

What intrigues me is the amount of brilliant people that seemed to work there. Imagine walking down the corridor and meeting all these oddities. Large amount of patents, inventions, great ideas, etc. Who were they?

Annually, Bell Labs also produced a rather big book (the “Bell Laboratories Record”)  with stories about their employees, their latest findings, etc. I have previously presented the fascinating story about the Swede and his wife.

Anyways. Going back to the naming of the transistor, which I also touched upon a while ago. Within Bell Labs they circulated a memo and had a vote about the name. The memo was MM-48-130-10, case file 38139-8 and can for example be found at


The list contains a set of people (here in alphabetic order). And what to do in late evenings than researching a bit on these guys (yes, all of them are male but the secretary Ms. XXX). Some of them are already so famous that they have gotten a wikipedia page. Therefore, I will only give a link and possibly some additional information for them. Some of the others were a bit more tricky to find information about. Some of them are also left in the darkness (i.e., not being on the internet). Some birthdates I had to find in civic registration records.

So, let’s go nerd!

1    J.A. Bardeen (1908/5/23 – 1991/1/30)

Well, one of the three… and might not need much more of introduction. Bardeen was a theorist.

2    H.L. Barney (1906/8/7 – 1960/12/30)

Harold L Barney worked with speech coding and a negative resistance device. He produced a paper with G. Peterson: “Control methods used in a study of vowels”. In the early days when bandwidth was sparse and increasing middle class with phone access, speech coding was a very important field of research.

3    J.A. Becker (1897/1/24-1961/7/13)

Joseph Adam Becker was born in Saar in Germany, came to America and studied at Cornell. He had some 20 patents (one of them on how to connect a resistor…)

4    H.S. Black (1898/4/14-1983/12/11)

Harold Stephen Black – the inventor of the negative-feedback amplifier and contributor to pulse-coding modulation techniques (PCM) for speech coding. Once again to be able to squeeze as many phone lines as possible into the same wire (and enable automated switch boards).

5    R. Bown (1891-1971/7)

Ralph Bown led the press conference that announced the invention of the transistor. He received the IEEE medal of honor and specialized in Radar and Radio.

6    W.H. Brattain (1902/2/10-1987/10/13)

Walter Houser Brattain, one of the three, was born in China. Needs no more introduction than that. Brattain is the older, more uncle-looking guy, in the lab-picture where Shockley has hi-jacked Bardeen’s microscope. Brattain was the experimentalist.

7    D.M. Chapin (1906/7/21-1995/1/19)

Daryl Muscott Chapin had a great idea. What if we could extract energy from the Sun into our semiconducting devices? He invented the silicon solar cell in 1954, the “solar battery”. Together with Fuller and Pearson he authored a rather famous article: “A New Silicon p-n Junction Photocell for Converting Solar Radiation into Electrical Power”.

8    E. Dickten (1904-)

Emil Dickten, Jr., also born in Germany. Together with Wallace and Schimpf (interesting name…) he authored a paper on “A Junction Transistor Tetrode for High-Frequency Use”. By adding a fourth terminal to bias the transistor higher gain at higher frequencies could be obtained.

9    J.O. Edson (1905-1970)

James Oliver Edson was a contributor to the so popular research on pulse-code modulation (PCM). He filed a few patents together with Black.

10    C.B. Feldman (1900-)

Carl Braft Henry Feldman studied at the University of Minnesota and then worked on steerable antennas at Bell. He worked on bandwidth-vs-transmission performance and was Shannon’s aid to formulate the channel capacity. He filed some 20 patents within the fields of antennas, PCM and transmission lines and authored papers with the famous H.T. Friis.

11    G.W. Gilman

George W. Gilman happens to share same with an inventor of pencils. “Our” Gilman, an MIT graduate, however, filed some 15 patents and worked typically on system’s engineering. He studied antennas and radio transmission.

12    F. Gray (1887/9/13-1969/5/23)

Frank Gray, the inventor of the Gray code, once again used for PCM. Gray also worked with television and filed quite a few patents.

13    H.C. Hart

Harry C Hart began working at Bell in 1939 and co-authored an interesting paper with Irven Travis on  analog computers.

  • H. C. Hart & I. Travis, “Mechanical solution of algebraic equations,” J. Franklin Inst., v. 215, 1938, p. 63-72.

The analog computers were designed to solve polynomial equations (root solver). He also designed an electronic harmonic synthesizer.

14    W.E. Kock (1909-1982)

Winston E. Kock later became the director of the NASA electronics research center (NASA ERC) and developed some of the first electronic musical organs!

15    J.G. Kreer (?-?)

John G. Kreer, Jr., is quite an unknown guy in the 31-man strong team. He has left some of his legacy in a paper

  • E. Peterson, J. G. Kreer, and L. A. Ware, “Regeneration Theory and Experiment,” Bell System Technical Journal 13 (October 1934): 680–700,

and he filed a handful of patents on various electronic circuitry.

16    C.O. Mallinckrodt (1907-1985)

Charles Olcoh Mallinckrodt probably had the coolest name among the crew. He also seemed to be an allround-type-of-guy and produced patents on both radio/wave transmission as well as companders and transistor circuits.

17    R.C. Mathes (1888-?)

Robert C Mathes was of Austrian descent and produced more than 50 patents! He typically worked with tubes, speech synthesis (PCM – anyone?) and frequency analysis. Mathes produced quite a few articles in the Boys’ Life magazine (scouts) on various topics. For example:

  • “Fun with a Pocket Compass – An Electrical Stunt that is Interesting and Helpful” (February 1914)


  • “Adventures in Electricity – Exciting Experiments With Your Static Machine”.

He also contributed to some of the refined first color television solutions. He was the most senior of the researchers and also jointed the BTL early.

18    J.W. McRae (1910-?)

James W McRae worked with transoceanic transmitter and is a recipient of the United States Legion of Merit.

19    L.A. Meacham (1908/9/3-?)

Larned Ames Meacham (also a cool name) invented the wobble organ in 1951 while not being busy with his work on PCM at BTL. Unfortunately, I could not find any clips with music played by this type of organ. More information you find at

20    S.E. Michaels  (?-?)

Another unknown in the team… S.E. Michaels authored a paper

  • L. A. Meacham and S. E. Michaels, “Observations of the Rapid Withdrawal of Stored Holes from Germanium Transistors and Varistors”, Phys. Rev. 78, 175 – Published 15 April 1950,

indicating that he worked in the measurement lab.

21    M.E. Mohr (1915/4/9-2000/7/17)

Milton E. Mohr, one of the youngsters in the team, filed a load of patents in various field of research. Given that I have worked quite extensively with data converters, I am quite happy to see Mohr’s name in the list. He constructed one of the first-ever quantizers. His Alma Mater was University of Wisconsin.

22    A.C. Norwine (?-?)

Andrew C. Norwine filed four patents with BTL and worked on pulse-code modulation. His patents related to coders and encoders. He found a clever way of doing an adaptive signal-to-noise ratio control, i.e., when there was less noise on the channel, the signal could be transmitted at less amplitude.

23    W.G. Pfann (1917/10/27-1982/10/22)

William Gardner Pfann was one of the outstanders – a chemist! He however played a very important role since he invented the zone melting process. This method enabled Bell to purify crystals, i.e., starting to produce high-quality semiconductors. For his deeds he also received the first Gordon E. Moore medal.

24    J.R. Pierce (1910/3/27-2002/4/2)

John Robinson Pierce is actually the key guy in this whole story, since he was the one coining the term “transistor”. He worked with Claude Shannon on channel capacity, traveling wave tubes and later relaying communication satellites.

25    R.K. Potter (?-?)

Ralph K Potter worked on frequency analysis of speech and how to be able to code speech more efficiently. He contributed to the theory of speech coding, worked for the NSA (since his techniques could also be used for cryptology). Perhaps most importantly, he is the mastermind behind:

  • “Frog Calls – the musical patterns produced by various species on a Summer night are made visible in traces”, published May 1, 1950.

26    A.J. Rack (1908-1988)

Aloïs J Rack produced a handful of patents on PCM decoders and radar implementations.

27    J.H. Scaff (1908-1980)

Jack Hall Scaff, a University of Michigan graduate, was a metallurgist and thus was contributing to the knowledge on how to dope the different materials used in the experiments and research.

28    J.N. Shive (1913/2/22-1984/6/1)

John N Shive refined the photo transistor and perhaps most importantly invented the Shive wave machine that could illustrate traveling waves. If not useful in theoretical work, it is an excellent way of illustrating standing waves, reflections, etc.

29    W. Shockley (1910-1989)

Shockley was the versatile guy, with the ideas to test and try, albeit a poor entrepreneur. Shockley does not need much more of introduction.

30    R.L. Wallace (1916/2/21-?)

Robert L Wallace, Jr., suggested that a point-contact transistor is not a practical component after all. This in turn led to the development of the junction transistor (also invented by Shockley). Wallace was a materials’ guy. Towards the end of this list, a quote from Wallace finds a good place:

“The advantage of the transistor is that it is inherently a small-size and low-power device,” noted Bell Labs circuit engineer Robert Wallace early in the 1950s. “This means you can pack a large number of them in a small space without excessive heat generation and achieve low propagation delays. And that’s what you need for logic applications. The significance of the transistor is not that it can replace the tube but that it can do things the vacuum tube could never do!”

31    J.R. Wilson (? – ?)

Also quite unknown after my research. He is not the main investor of Xerox, though (same name)… J.R. Wilson worked with Radar at Bell Labs and if nothing else, so far, we can get a glimpse of him at

Looks like a nice man overviewing the youngster’s experiments in the lab.



Top ten sensors to further develop or add to the smart phone

I have touched upon this subject before: sensors in smart phones. In my opinion, the development towards implementing the all-round tricorder has somewhat halted. Phone manufacturers are focusing on improving speed, power consumption, standby-time, etc., which of course is good, but the driver is not that clear to me. Surf faster on your favorite news web portal? Watch youtube videos? Play in-app purchase games? Take photos with crap cameras? Ubiquitous computing?

So, where is all that useful stuff? The things that would make your phone a real companion in your back pocket. To be used in the kitchen, during the walk in the forest, when DIY-ing or mcgyvering, etc.

In this post, I list the Top Ten sensors (well, …) I would like to see implemented in a phone quite soon. As far as I can see, a lot of technology and hardware is already there, so why not start expanding and combining it?

With that said, some of the listed sensors already today exist as 2nd- and/or 3rd-party products that can be attached to, or wirelessly connect to your phone. But still, integration would be desired. Further on, some of the applications for the different listed sensors do overlap, I am aware of that, but they could also be complemeting each other and further strengthen the combination.

image01With the risk of missing some, but to the best of my understanding, the following sensors are available on the Samsung Galaxy S5:

  • Vision (Camera)
  • Sound (Microphone)
  • Location (GPS)
  • Accelerometer
  • Gyroscope
  • Gravity
  • Light (Diode)
  • Orientation (Compass)
  • Magnetic field
  • Atmospheric pressure
  • Proximity (diode)
  • (Notably missing: Thermometer and Humidity – available in Samsung S4, though)

which are perhaps more than one would first think is actually found in your phone. On Google Play some of these sensors are utilized for first-order versions of the sensors listed below. However, the accuracy is quite low and it calls for improvements. See the snapshot from one of the apps in the play store.

I have deliberately not put focus on health sensors, such as heartbeat, etc. There a lot of things are happening and would probably fill this list by themselves: spirometer, oxymeter, and so on. I have not listed mind-reading devices and polygraphs either, for that matter, and notably omitting the age detector.

(Doppler) Radar

image02Some week ago I had a visit by Prof. Dag T Wisland from Oslo University and Novelda AS in Norway. Novelda manufacturers a low-power ultra-wideband radar module, the Xethru. See their web page at https://www.xethru.com/ The device consumes 120mW and is comparatively compact. (This is the transceiver, additional computing is of course required by SoC and software in apps).

Novelda suggests more practical applications by utilizing the phase shift due to the doppler effect: presence detection, respiration detection, etc. Place your phone on the kitchen table and use it as an alarm. Wake-up detector for your sleeping children.

Or, why not become an expert in finding the beams and wiring and pipes behind the wall? That would impress your spouse (well, …) if you can assemble that IKEA wardrobes and fit to the wall without any mishaps. Bosch offers these kind of devices:

I want that integrated with my smart phone – and imagine what a cool app you could have.

Ultrasonic transceiver

Using an ultrasonic transceiver is quite a similar idea to the one above, I guess: a way to look inside objects. I admit, if it is used to see inside your body, the phone might become a bit gooey when you put that conductive gel on. But in fact, ultrasound can be used for other things: ranging, non-destructive inspection to look for cracks, and even communication.

Could the plummer use it to inspect the pipes after welding? Could the home-cook use it to check the bread – has it proved enough?

With ultrasonic microphones and speakers in e.g. a room, the phone can be used to quite accurately find out its own position and also the positions of other objects. The optimum sheng fui garage could finally become true:


I would like a more accurate thermometer (and in S5 I do not have one anyway). Now and then we need to take the  temperature and check for a fever or so (hard to push the phone into your ear though, but nevertheless). Also the ambience temperature is of interest. It could be a matter of logging the temperature in my  house to adjust the indoor temperature or opt for closing a window. This could be used to lower the energy consumption in my house (assuming that your already-installed heating system is not optimized). But also more practical things: what is the temperature of my christmas caramel? Or bakery in general.

Some apps are already available on Google Play and small ambient thermometers are for example sold by http://thermodo.com/ in Denmark. Similar devices are available for ear thermometers. Powered and read out through the audio interface.

The thermometer does not necessarily need to be a thermistor, but could also be supported by IR camera – if it would be portable enough. Products for smart phones are already sold by eg.

Photo- and laser diodes measuring longer distances and angles

Now and then I need to align some paintings or shelves to be mounted on a wall. Or find the center point on a wall, beneath a painting, or similar. This would be a way to complement the plane leveling-alignment laser, like for example Bosch sells too. There are apps measuring angles and distances given a couple of photos, gyro settings, etc.


With more intelligent software (and hardware) to control the laser pointer we could have the device “paint” the target on the wall directly. Let the phone auto-orient by identifying points through the camera or ultrasonic localization. Angles, distances, etc., could be measured and stored. Cleverly combining the diode and the camera could offer you to measure distances of complex objects.

A square box could indicate the boundaries for the placement of your latest diploma. The laser could be used to paint the actual time in the roof above your bed. It could be used for games and entertainment of many kinds. (But that is on the other hand not the path we want to go down in this post).


Already today, vibrations can be picked up by the accelerometer of the phone, and there is academic work out there describing how the accelerometer can be used for the purpose. For example, measuring the vibrations of machinery can be used to monitor the structural health of the device.

For more domestic applications the vibration in the washing machine could be logged to determine when the machine is ready. Earthquakes or traffic vibration, or for the handyman to check vibrations in pipes and ventilation could be used.

Perhaps it could be used in the car to detect and report quality of the road and in general give feedback on your car’s health and guide you towards service of the car.


The Samsung S4, for example, sports a humidity sensor. Use a phone to check the humidity health of your house or crowd-sense data and upload to the weather services. While sleeping at night or idling – let the phone collect information while still charging and doing nothing useful.

Those with sensitive skin are dependent on a healthy humidity level. With your phone you could more actively control a humidifier and let it adjust the level as per your presence in the house. Active humidification!

Metal detector

The phone does already today offer a magnetic sensor that can detect the field and disturbances in the force. The magnetic sensor in the phone will vary with presence of objects that alter the magnetic field. With the metal detector we can look for nails behind the wall, electrical wiring, pipes, “lost” wedding rings in the sand, etc.

Imagine you could finally get that superman power and see straight through objects. (Unless it is cryptonite, of course)! An xray could do the job for you, but I admit it would be hard to implement since you need to have a detector on the other side of the object or perhaps rely on microwaves and ultrasonic inspection. Then we’re back on list items 1 and 2 above.

Still though it would be practical to have right in the palm of your hand.

2016-02-29 11.10.24Scale

Weighing things has been integral for quite some time now. And wouldn’t it be good to be able to measure the correct amount of sugar for your cake? Pour up the sugar in a bowl and put it on the phone. Remove the bowl and the weight is displayed in the window.

In fact, a few phones (like my Samsung S5) does have a (air) pressure sensor and indirectly it could be used to measure the weight. In fact, there are (of course) apps out there that implement this – to a limited degree of success, perhaps. But who’s to blame, the handles are not really in place yet.

One would argue: why put an expensive phone in the kitchen and expose it to to water, fat, and grease? Good question, but consider this: the Sony Experia E4G, now cost approximately $70 dollars in Sweden. It is not water proof, but that’s semantics. The price is low and almost expendable.


Gas could be dangerous. Anyone who lives with (or works in the same cubicle as) someone that enjoys baked beans, onion, and lentils know that by now. Jokes aside. Mould, fungus, and moist could also be dangerous to your health (and to your house). A gas sensor in your phone would be able to sniff around the house and report any levels of strange gases.

To no surprise (?) there are third-party devices that can be connected to your smart phone to do the job. For example sensorcon, http://sensorcon.com/, does this. In fact, they have a sensor package that can do quite a few analysis in parallel.

At home, the gas sensor can also be used to detect smoke, checking if the cinnamon rolls are done or not, or indicating if you used too much perfume (or too little deodorant).


With a spectrometer you can measure the contents of a “foreign” object. See for example what Analog Devices currently is developing together with an Israeli startup :  a set of “market hand-held scanners that can be pointed at food or medicine to detect what’s inside.”

This is close to what the tricorder could do in the star trek movies. Just let the device scan the object and see what it is made of.  Other devices are suggested by commercial entities out there, such as the near infra-red spectrometer.

On handing in assignments on time

Now, while still waiting for assignments to be handed in from courses, thesis, etc., I stipulate a hypothesis (or whatever a mathematician would say):

  1. Let time point TA be the time that the examiner suggests as a submission date for an assignment.
  2. Let time point TB be the time at which the student finally hands in the assignment.
  3. Let time point TC be the critical time point at which assignment must be marked (as per the student).

Then, my hypothesis is

The ratio TC-TB over TB-TA will rapidly approach zero.





The transistor symbol

Together with Maple Martin I browsed through our group’s library and came across a couple of books by Prof. Kjell Jeppsson (from Chalmers University of Technology). One of the books, “Praktisk transistorteknik” (1965), triggered me – of course. Browsing through the pages, I realize that the transistor symbol he used in his figures looked unfamiliar to me. It was the 1965 version of the Swedish standard symbol for the junction transistor.

Where does the symbol come from? My short-story/interpretation.

So, in case you might be taking the course in analog electronics at the moment: this post aligns quite well with the topic we are currently reading. Take a quick glance at my impressionistic skills below. I have depicted the first point-contact transistor (to the left) and the “first” junction transistor (to the right). It is pretty obvious from where the – today, widely used – bipolar symbol comes. The symbol is found at the bottom left of the picture. Above that my redrawing of the famous Bell Labs photo. The v-shaped piece of plastic, on which the phosphor-bronze traces where applied, guides the emitter and collector to and from the germanium plate which is attached to the metal frame which the base in turn is connected to. The “housing” around the transistor is modeled by a circle around the lines.

To the right in the picture, we see a sketch of the junction transistor. A more homogeneous solution. From left to right we have the emitter, base, and collector. Here the currents go “through” the semiconductor whereas in the point contact transistor it goes on the surface (well, arguably, but true to a first degree …). Looking at the international symbol, it does not really make sense – if one has time to care about those kind of things. The Swedish standard institute (SSI) symbol, from 1965, is depicted below the junction transistor. It turns out to be a bit more of logic behind that one. The base “cuts” the emitter and collector and the current goes straight through the base. However, the symbol lost the battle.

Transistor symbols

Transistor symbols

I guess the thing was that the junction transistor was invented and patented quite soon after the delivery of the 1947 Christmas present in the shape of a point-contact transistor at Bell labs. Due to the more integrated nature of the junction transistor it was also a better choice for most users. In addition, the junction transistor has much higher gain (200 vs 20), was less noisy, and could take on higher power levels. (Not as high as for tubes which were even faster. In fact the point-contact transistor initially had a higher gain-bandwidth product.). Due to this rapid development, the old symbol made it into the books. There was no point in developing a new one (unless it was exported to another continent).

Feedback – a quick overview

Feedback is a very important concept in electronics, or systems, or biology, or … Well, feedback is important. Period. And even if we do not intentionally design with feedback – there will be feedback anyway. Through parasitic paths or through bias wires or common rails of different kinds.

Explaining (negative) feedback in detail – negative feedback is a positive thing – positive feedback is a negative thing – does not make sense here. There are essentially millions of resources out there going through all this.

Instead, in this post, I just present a picture that I did the other day. It compiles the four passive (well, …) fundamental feedback modes that you can expect to encounter. The four cases are essentially given by the dualities we have: Voltage/Current and Input/Output, i.e., 2 times 2 = 4 cases. The picture is there to illustrate the fundamental properties on a “low” level. As mentioned: there is so much, much more to dig into when it comes to feedback.

One can understand that H.S. Black had some work to do after he got inspired by Steinmetz. Steinmetz, btw, was also involved in the group pictures post the other day. They all seemed to know each other. (Speaking of that Mr. Black was also part of the team that coined the term “transistor”).

Anyway, for future quick-reference, here are four examples of feedback with some simple properties compiled in a two-by-two matrix. Beta is the feedback factor and H is the system transfer function. Some of the examples contain IV and VI conversion which in some sense obscures the feedback. I have indicated those – I hope.