Brought To You in cooperation with the Musée des Arts et Métiers - Paris.

The aerial telegraph  created by Claude Chappe (1794) is a means of optical communication. The telegraphic network  was made up of a succession of semaphores perched atop towers that were 6 to 12 kilometers apart. The position of the semaphore wings indicated a coded message to be transmitted. Each such position corresponded to a number which directed the receiver to a specific page in a notebook where the message in letters  could  be found.

A microphone is a transducer that converts a mechanical (acoustic) wave to an electrical signal. From this point of view,  it is the symmetrical oppposite of  a loudspeaker. There are different types of microphones. In each case, we find something vibrating under the influence of a sound wave and the use of a physical law to convert this mechanical vibration to an electric signal.

The modulation of a signal is essential if one wishes to transmit it over long distances.  Modulation  also provides a means for simultaneous transmission of several signals, using the same transmission channel (Hertzian, cable ...).

Amplitude Modulation (AM) is the simplest and the oldest of modulation methods, primarily because the stage of demodulation, at the receiver, is simple to carry out.  A modulator, followed by a filter, is sufficient to obtain an amplitude modulated signal, but it should be pointed out that this type of modulation generates numerous distortions and so frequency modulation (FM)   is now the preferred modulation method.

The digitization of an analogue signal is carried out by taking several samples and translating them into binary code.  The series of codes thus obtained are then regrouped in a digital file. The advantage of such digitization lies in the ability of such file formats to undergo processing  by a computer.  In order to obtain a digitization that corresponds to the original analogue signal one must gain precision. To do this, it is sufficient to increase the sampling frequency and decrease the pace of quantization.

It is because demodulation of an amplitude modulated (AM) signal is so simple that this type of modulation has existed for so long. The fabrication of a simple envelope detection circuit  like that shown in this simulation is very simple and not costly.

Nonetheless, the rectification provided by a commutation diode produces some distortion, and this type of circuit is no longer used in high quality receivers.

A loudspeaker is a system that transforms an electric signal into a mechanical signal. At the heart of this system we find a coil made of conducting wire, carrying an electrical current, which moves  under the effects of magnetic forces. A flexible membrane (or diaphragm), attached to the coil, acts like a piston that pushes the surrounding air. This animation has been slowed down many thousands of times -- audible signals lie between 20 and 20,000 Hz.

There are, in fact, several Moore’s Laws. At the beginning, Gordon Moore, an engineer with Fairchild Semiconductor (a co-founder of Intel) showed in 1965 that the number of transistors per semi-conductor component would double every 18 months, at a constant price.  But, very quickly, different Moore’s Laws would emerge to characterize the exponential growth in calculating power, density, complexity…

This animation represents the evolution over time of the number of transistors per component (microprocessor)  The ordinate is graduated with  a logarithmic scale. Thus, this truly shows an exponential growth rate.

We are currently in a slowdown phase where the criterion of density is concerned (thermal dissipation, quantum effects) and so the growth of this curve is slowing down.