Information Theory

From the first Postmails, Birds, Steam, Telegraphs, or Antennas: Communication was vital.

During the time of Anne Frank, it was necessary for anyone in school to learn "How to build a radio". Not only to show a counting symbol "I am here" or show another ship the location or for emergency steam.
It has also the possibility to bring entertainment into the house of many lonely souls.
When the Titanic sank down (1912), most of the people screamed or rushed into the boats.
The life-saving signal came from the first few Marconi Antennas. (just after Heinrich Hertz founded them)

The measurement methods via sharper lenses, compasses, or gyroscopes didn't need more reliance, but the transatlantic signals saved and showed many ways via technology.
The controlled steam engines of the ships (measuring the speed at the own rivers before calculated), might have needed more reliable navigation.
Hence additionally these previous techniques were adapted on a smaller scale for the first flying airplanes.
> As well in wages of war or in combat against crime.

Thus, the invention of the first telegraphs helped to transfer information about a murderer inside a train. Later police station received their own frequencies for communication and later also the teams for natural catastrophes protection.

For most people, on the other hand, was the radio until today the biggest influence. (f.e. German Radios(19centuary, Japanese smaller Electronic Radios(1950ties) It brought the voice into the households.
Thus also Orchester or Opera.
Written with "AM" or "FM" Radio Waves were part of the Car Roads while listening to the frequency rhythms of Jazz Music. Some went even hiking and wondered, why through the thickest mountains, they could still hear Radio Signals. 

Thus, Engineers have stretched the effect of higher frequencies (beyond LUT until MUT).  until these are reflected back by the Ionosphere itself to earth. Even through mountains, one can receive a signal simply because the smallest (ε & μ) of the medium (air)  bend the wave such, that you'll receive kilometers afar the reflected signals. ('Diffraction'. Fairly notable: The effect gets reduced with higher frequencies(MUT)).

High-frequency waves for satellite communication helped radar but as well to reach as - humans - the moon during the Apollo Mission (1969), it enabled as well the view into the microscopy [μm ] worlds of Materials [=10e-6], as well as Nanometer [nm] scaled Molecules [=10e-9].

On the other side (1) ultraviolet light, (2) Röntgen Radiation, (3) cosmic Radiation, and (3) Meteorstorms, that burn up inside the earth's atmosphere take part in the Ionisation of neutral O2- Molecules.  Under an amount and 'Recombination', the atmosphere turns into an electric conductor and thus reflects Electromagnetic  Waves on a specific frequency range. It isn't exactly a Reflection process, because it doesn't happen abruptly, but over time. It leads to a change in the 'Dielectric Constant'. ('Refraction'), which also leads to a different speed of the EM-wave.
>Not Diffraction)

Even broader at the scale of each of our own pocket devices. Communication meant the next scale for a fairer distributed measure to anyone at scale. 

Libraries, which were privileges in households or storage in the filtered form became free in every child's hand, like mine. Thanks to the Internet.

Notable: The Main 'Current' in Communication is the 'data' stream.
How much data can everyone send per time? The computer science student uses Byte/second for the Memory, that is extracted.
But true Electric Engineers use Bit/s to demonstrate the data stream.
Hence Byte/s is used for storage devices in one device.
Bit/s is used for transmission between devices.
The 'Bandwidth' explains the physical min-max (frequency spectrum) of the data, that can be sent.
datastream. (download/upload)

What is the minimum data size (without creating errors), that every computer can be sent in the network? (to be the most optimal energy-efficient network)
This minimum of redundancy, which leads to maximum data rates (Shannon Limit) is crucial. Everyone sends this minimum. Else there would be traffic crashes. During 9,6Kbit/s, it wasn't possible to transfer higher data rates, unless you enhanced additional data to maximize the data rate. Thus redundancy is necessary. (Unlike many people, who see it negatively, like some computer students, who haven't read Shannon- Information Theory.) -> LDPC
Another key is Compression or Encryption. (also by Shannon)
Speical Fouriertransformation like the Hilbert & Wavelet transform are also of use.

Notable: 5G and 6G, as well as Higher Satellite Communication, is on the march. If you regard some IEEE articles, then you'll witness that even the heartbeat can be read out via a Wifi Signal.
High Bitrate is referred to as the number of Data lines multiplied by the Bandwidth (Frequency spectrum, higher-lower frequency spectrum.)
Signals get modulated and the stochastic distribution is Gaußian Noise in general and in semiconductors even Poisson Noise.
In Communication Engineering a high Signal to Noise ratio is preferred and reliability is of the essence.
Non-Stationary Signals are distributed finer and it is unknown whether the brain works in these modulation schemes..
> Theta Signals are here the current hopes.