Category Archives: Ciencias

The invention of the telephone.


On June 25, 1876, Alexander Graham Bell demonstrated the prototype of its new invention, the telephone and it is this apparatus that I’m talking about today.

“TelephonePatentDrawingBell” by Alexander Graham Bell – This media is available in the holdings of the National Archives and Records Administration

We are not going into a controversy of who actually invented the telephone and the reasons why Antonio Meucci (who had begun the process of its patent years earlier) and Elisha Gray failed to patent it before. The fact is that the patent was issued to Bell on March 7, 1876.

Bell had great knowledge of acoustics and voice modulation as his mother and wife were deaf, and his father, grandfather and uncle were all elocutionists.

For many years he focused his efforts in trying to transmit sound through electric means.

In 1874 while trying to develop a harmonic telegraph, his assistant Thomas A. Watson discovered that could transmit more than one note using iron membranes driven by electromagnets. Bell immediately saw the possibilities it offered them and began to develop a new device to transmit voice.

Primer diseño de teléfono.

In 1875 they built the first model (shown in the photo at left) that did not really work.

After some experiments and modifications, including a membrane of little harder iron, or a liquid transmitter, Bell decided to patent it (even without many details of the invention) seeing that it was viable (with quite discreet results).

On March 7, 1876 he was awarded with the patent and starts experimenting again. Only three days later, on March 10, managed to transmit the first words to his assistant who were in another room.

This page in his laboratory notebook records the event:

Biblioteca del congreso Diario de laboratorio de Graham Bell. Dia 10 de Marzo de 1876.

“I then shouted into M [the mouthpiece] the following sentence: ‘Mr. Watson–come here–I want to see you.’ To my delight he came and declared that he had heard and understood what I said. “.

The demonstration that took place in the Universal Exhibition in Philadelphia, announced the invention to the world and the news caught the press at the time.

In November 26, 1876 the first telephone conversation between the cities of Boston and Salem, Massachusetts, at a distance of 16 miles is performed.

One of the two phones that were used at that time is in the National Museum of American History (Smithsonian).

Bell's Large box telephon Bell box telephone.

Bell's Large box telephon Bell box telephone.

It consisted of an iron diaphragm, two iron core coils and a permanent horseshoe magnet.

As described by the museum itself:

“When used as a transmitter, sound waves at the mouthpiece cause the diaphragm to move, inducing a fluctuating current in the electromagnets. This current is conducted over wires to a similar instrument, acting as a receiver. There, the fluctuating current in the electromagnets causes the diaphragm to move, producing air vibrations that can be heard by the ear. This was a marginal arrangement, but it worked well enough to be employed in the first commercial services in 1877. The magneto receiver continued to be used, but the transmitters were soon replaced by a carbon variable-resistance device designed by Francis Blake and based on a principle patented by Thomas Edison.”

And this is where we present our work.

With the invaluable assistance of my father (Jose Manuel Corral Rodriguez), who has developed and built with us this model (and here we thank him), we have built a working replica of the first commercial model.

1 (Large)

6 (Large)

Although some elements have been modified to replace by modern pieces (like magnets), the external appearance is the same as the original.

Here’s a soundcheck:

17 (Large)16 (Large)14 (Large)12 (Large)8 (Large)

As explained in the description of the Smithsonian, soon using this model as a transmitter and receiver, they decided to adopt the carbon microphone, thanks to which they could hear much better.

We have also constructed a (not replica) device to use one of these microphones without the need to have two copies of the phone.


Together with some 32 feet cable, to be able to move away enough so that you can hear the device itself, not the raw voice.

You can buy one of our replicas in our store.


A toy for sharing with our daughter

On this occasion we suggest you to make a toy for your kids to share your workspace, is that, even though the Three Kings just left their gifts, our daughter (as is usual in children) seems to have more fun playing with our things as with hers, and since she learned to whistle the multimeter (set to check continuity), every time she has it on hand what, she brings it asking us to turn it on.

It’s been a while since the last time we wrote, and we apologize for that.

It’s been a hard time for our family, but gradually return to normal.

As there seems not very reasonable to let a toddler to click anywhere, I decided to do a toy to make the tester whistle while we work.

It is a simple game to find pairs, touching at points that are connected together.

While it is true that in order to play you must have a multimeter at home (and not everyone has it) it can be done with any broken toy at home, after all this wiring will replace the switch. Anyway this toy has been specifically made to take advantage of the interest that our daughter has in the multimetermeter and will be used under supervision, children should not play with these things if we do not know what we do.

We need a table, fat cardboard or sheet of any material (which does not conduct electricity, of course), images in couples to stick on the table, rivets with tab, cables, soldering iron, tin, hot glue and something to cover the cables behind when finished.

It’s actually so simple that needs little explanation, so I leave the pictures and little else.

1.- PVC table and stickers.


2.-Stickers placed randomly (half right and left but messy)


3.- For each rivet a hole (3mm) is made and inserted next to each sticker.


To prevent them from turning and thus can remove the cables, I glued each rivet  with hot glue.


This is the look ahead:

resized_frontal4.- When wiring, I try to stay wires tidy and hold them with glue. Be welded on each side, or if we don’t have a welder, you can wrap the cord at the ends of the rivets and secure with silicone.


5.- Finally we cover the wired surface with felt, foam or EVA which is what I used, so they are no wires and ends in view, and does not spoil. Then I fixed the edges with masking tape.


That’s it, ready to play, match and beep all she wants, and when we use the tester, María can make use of it and have fun with us.



And besides of having fun, she is slowly making contact with these things as I did as a child.

This reminds me, by the way, a work I did in school, that time when we were sent to make a simple circuit that would light a bulb, and I (with advice from my father, of course) made a map of Spain that lighted up when you matched each province with its name … the result was that the teacher said that I had not done it …. And I said (with all my tranquility) that if she wanted the next day I would carry the materials to class and taught her to do it. Finally she let it go.

Pythagorean Theorem




“In any right triangle the square of the hypotenuse equals the sum of the squares of the legs.” Pythagoras of Samos

Demostración de Euclides
Demostración de Euclides

There are hundreds of demonstrations of this theorem (ES Loomis, cataloged 367 different tests, other authors speak of 1000), more than any other mathematical theorem. These tests have been designed by people from very different condition from which a Babylonian magician, a student from Ohio 14 years old with a normal intellectual level, the math genius 21 Galois and  James A. Garfield, who became president of the United States in 1881.

Chou-Pei Suan-Ching (hacia el 300 a.n.e.)
Chou-Pei Suan-Ching (hacia el 300 a.n.e.)

A persistent tradition documentary based on Vitruvius, Plutarch, Diogenes Laertius, Ateneo and Proclus, the Pythagorean Theorem attributed to Pythagoras himself. But archaeological discoveries of the remains of the cultures of Mesopotamia, Egypt, India and China, have revealed that these civilizations known aspects of the Pythagorean Theorem many centuries before this wise. The references of  this pre-Hellenic Theorem don’t contain , however, tests of the same, while it is generally believed that it was Pythagoras (or any of his disciples) the first to provide a logical proof of Theorem, which will make it right there passed into history with his name.

Demostración de Perigal
Demostración de Perigal

Another important reason for the large number of existing demonstrations reason is that in the Middle Ages a new demonstration was required to achieve the degree of “Master Matheseos”. We found more or less intuitive, algebraic, geometric and graphic demonstrations, (Pythagorean puzzles). Even art has caught the spirit of this theorem, which has inspired many artists.

William P. Haas, La visión de Pitágoras (1993)
William P. Haas, La visión de Pitágoras (1993)

From encouraged us to build one of the simplest, so that at a glance and in a fun way we can verify that indeed, if a right triangle has legs of lengths a and b, and the measure of the hypotenuse is c, states that:

                                            c^2 = a^2 + b^2 \,

Here we present our practical demonstration on a fridge magnet. We just have to turn it to fill the surfaces (volumes, but for the visual effects we take them as surfaces) of the legs or the hypotenuse respectively.

Pythagorean Theorem demonstration

It works like an hourglass, a mathematical clock ….
pi1 (Large) pi2 (Large) pi3 (Large)It is available in our store, if you belong to a school or other group interested in buying multiple units please contact us so that you make a budget. (Pythagoras Magnet from MJ2Artesanos).