Mar 31, 2015

Engineering Explains It All: The Numbers on Your Phone

What can engineering teach you? Interlace it with history and it can explain the world as you know it (or knew it).

I was having lunch with a friend and somehow phones came up. Suddenly, she said, "I never understood how that switchboard thing worked."
Image by Dan Shirley, via

So I explained that in the old days, phone were for the rich, with a direct line from one place to another, like the drawing room and the servants' quarters. If you wanted to connect two other places, you bought another phone line, which would connect, say the master bedroom to the servants' quarters. So some places, like the servants' quarters, would have multiple phone lines. This didn't seem weird as that's how the old bell system worked, when you would ring for the butler.

If one rich person wanted to connect to another rich person, then a line was set up from one house to another. Eventually, when more phones became prevalent, and one person wanted to anyone who happened to have a phone, the switchboard idea came into play. Basically, all the phone wires would come into the switchboard. Simply put, the switchboard provides a human a way of connecting two phones together so they can communicate.

Generally, speaking, a person would turn a hand crank on the phone to "ring" the operator at the switchboard. She (usually a she) would insert a plug into your line and connect so she could talk with you. Then she would ask you who you wanted to talk with. If you wanted to call up the grocer, then she would plug go to the grocer line, ring that phone line and make sure there was someone there. Then the operator would plug a wire into your line and the grocer's and thereby connect you.

A small town switchboard could have a number of lines coming in. If you wanted to call someone in another town, the operator would connect to that outside switchboard's operator. That operator would connect with the person you were calling, and then wires would be plugged into connect the phones up.

If you think of a city as a series of small towns, you can see that giving each phone a number, rather than a name, may make things easier for an operator in your area of the city. But if you wanted to call another area, you would also need to indicate the area of town you were trying to call in addition to the phone's number. Hence, the movie titled "Call Northside 777" referred to a phone number. Eventually, there were too many areas, and automated switching was developed where people could get automatically connected by typing in the number for the area, followed by the number for the phone. But how would people know which three numbers to enter?

Enter the idea of letters on the phone. With our example, Northside, you would find the first three letters on the phone (NOR) and press the corresponding number: 667. This was known as the exchange number, and this protocol explains why the old land lines in the same area of town often have the same first three numbers. We started to lose this idea as more phones came up in an area, and numbers that didn't correspond to the area name were added.

Other dialing protocols can be explained by the automatic switching, too. For example:

  • Dialing 1 for a long distance call
  • Area codes (in the old days) having a 0 or 1 as the middle digit

For those of us who remember landline phone numbers, this really sheds light on our world, and thereby gives us an instinct for reverse engineering phone switching technology. Pity the poor millennial who not only doesn't have this history to intuit how automated systems work, but also doesn't know why phones "ring"...

See also:

  • North American Numbering Plan, Wikipedia for explanations on the rules around phone numbers in the old days
  • Switchboards, Old and New, At&T Archives for pictures of the old switchboard systems and some trivia around the switching system (e.g. boys were deemed poor operators because of the pranks and cussing they did with the callers)

Mar 17, 2015

Tibetan Monks Go to College: STEM and Religion

Six years ago, I stumbled across a New York Times article about Tibetan monks and nuns learning science. It was part of the Dalai Lama's attempt to keep "modern and relevant" while honoring the Buddhist tradition. In a time when religion is often pitted as the antithesis of science and math, it was inspiring to see a spiritual leader articulate the commonalities, citing "investigative approaches with the same greater goal of seeking truth."
image by ndigit, via

Since then, more has been publicized on the experience of the monks as they journeyed to Emory University to learn more and of the professors who were challenged by students with limited English and formal education but who are "sophisticated adult learners" who are used to working through difficult ideas and analyzing contradictory observations and teachings. One of the most fascinating things is how do you teach students with no former experience with the scientific method.

You can see samples of the lessons and activities on their Science for Monks website, and a video about the experience at Emory University. While the monks certainly learned (and challenged) their science professors, the professors learned quite a bit from the monks as is documented by Chris Impey's Humble Before the Void which certainly looks like an interesting read for those interested in the intersection of religion, science, and philosophy.

So for those who have added R to their coursework in STEM, this project may provide an interesting resource and perspective.

Mar 3, 2015

Language and Math: Thoughts from Piraha Studies Regarding Language, Comfort, and Recursion

Back when I was teaching Computer Science, I ran across an anthropology article (Science News, The Piraha Challenge) about a research team who tried to teach the Amazon Piraha tribe math and reading. Two particular aspects seemed particularly relevant to me both in teaching computer science and later engineering and STEM.

image by mimwickett (Miriam Wickett), via


The Everett's, Daniel and Keren, worked with the Piraha in the late 70s to learn more about their language. In the early 80's the Piraha asked them to teach them to count and to read. Eventually, though, both lessons ceased. 

The article explains the discussion among anthropologists and linguists about language and culture roles in the situation. With math, the fact that the Piraha language had only words that roughly meant one, two, and many made simple arithmetic difficult for them. With both lessons, it seemed that practices required to read and do math conflicted with their "cultural conviction on how to converse."


Most notable was the belief that one should only talk from one's own personal experience. This eliminated language around "abstract concepts or ... distant places and times." In fact, trying to do so may have caused discomfort.

Think about it from a STEM point of view. The most basic mathematics problem is: "If I have two apples, and you give me another, how many will I have?" This concept requires thinking about something that does not yet exist in the real world--and in math, this is just the beginning of abstraction. If your student's culture feels this practice is wrong, success in the field will be difficult.

As a teacher, observing the student was just as important to me as communicating concepts and practices. When a student struggles, I always have to ask myself (or the student, if the right rapport is set up), "Why is this hard?" My job as a teacher is to then use this insight to make the subject make sense to the student. This is why teaching is an art, and really good teachers cannot be replaced by simple (or even complex) programs. 

This idea that a culture may actually feel that the typical practices of the subjects I taught would border immoral was fascinating to me. And perplexing. I don't think there is one, catch-all solution to it, but I share it here so other good teachers may at least consider it as they develop their lessons and teach their students.


One of the aspects the Everetts note is that the Piraha have no recursion in their language. There was some debate about this, but to me, the more interesting aspect is that recursion occurs in language.

My experience with recursion has always been in mathematics and computers. In fact, I was teaching a lesson on recursion the week I read this article, so I brought it up with my math majors, some of whom had already been introduced to it in their discrete mathematics course.

In case you don't know, in math, recursion is a process or definition that is really very simple: It has a general procedure that calls itself, using the next item in the series of numbers it will be applied to. It also has a termination condition. It's probably clearer with an example. Factorial is the most common example of a recursion function: When calculating the factorial of n, a number greater than 0:

  • See if n is 1. If it is, then the answer is 1.
  • If it isn't, then multiply n by the factorial of n-1
This means that 
  • the factorial of 1 is 1
  • the factorial of 2 is 2 times the factorial of 1 (which we see from above is 1) so it is 2 times 1 or 2
  • the factorial of 3 is 3 times the factorial of 2 (which we see from above is 2) so it is 3 time 2 or 6
  • etc.
In computer science, this concept is related to the stack data structure, and is one of the first standard algorithms taught. It was a very power concept in the early days of programming when memory was expensive because the code was tight, but the range was largely infinite.

But students always struggle with it. If you're a standard programmer (not a computer science major), you may be able to go through your whole life without ever using it. I've come up with a few techniques to explain how to design and decipher recursion functions, but there was always a struggle with the first grasp of the concept. If students don't feel that they have an inkling of the idea at the start, the rest becomes a struggle to memorize the bits and pieces they do get.

One of the key elements in recursion (and when implementing it in the computer) is that some information must be "held" until the next step is completed. In the case of the factorial, we know that factorial of 100 is 100 times the factorial of 99, but we have to hold that idea until we find out the factorial of 99, which requires us to wait until we figure out the factorial of 98, etc. Basically, we don't know the answer until we get the problem to be the factorial of 1, and then we can go back to all the multiplications we "held on to" until we got the answer.

This sounds daunting to a student. So I brought up this idea of recursion in the language. They were intrigued, and for some, it was a more gentle introduction to the nut graph of recursion.

Recursion in the English language can be easily seen in two places: 
  • Clauses: Consider the sentence "When I'm doing eating, we'll go to the store." You have to "hold" the data of "When I'm done eating" before you get the the main idea which is that we're going to the store. This makes me wonder if the Germans are particularly good at recursion because the active verb doesn't usually appear until the end of the sentence. Used to drive me bonkers. But in a way, it makes me realize that the action verb is very important to my understanding of the sentence. Perhaps the German mind soaks up more from all those other words and the verb is just a final concept to the mix.
  • Relatives: Consider the fact that the mother of your mother (a recursive relationship) is your grandmother. The mother of your grandmother is your great-grandmother, and then, it becomes just a matter of how many "great"s you need: great-great-grandmother, great-great-great-grandmother. The Piraha have a word for mother and then refer to their grandmother by given name. The language doesn't have this recursive relationship and therefore, it may influence the models and relationships for other ideas. 
Other studies seem to show strong links of language to STEM skills. Many studies I've been reading regarding spatial skills seem to indicate the importance of using spatial words early and often with young children. Even popular writer, Malcolm Gladwell, brought up language and math in his book Outliers:  The Chinese way of counting has a distinct pattern that correlates to the base 10 concept. Compare this to the English way of counting: The translated phrase for 11 is ten-one (not eleven), 12 is ten-two (not twelve), 20 is two-ten (not twenty) and 21 is two-ten-one (not twenty one), etc. This consistency of the language pattern may be helpful when learning numeracy.


Too often, I hear from colleagues that there is a battle between the literacy folks in education and the STEM ones. Research like this show that it's not an either-or, but a tight partnership. The next advances in STEM education need to happen hand-in-hand with the literacy education. Both are important, and they help each other. So why not work together?

~ Until next time, Yvonne

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