Communicating at a distance, from Greek "tele" for distance!

A very cool thing about telecommunication is, besides how incredibly fast it advanced (in this sense it is no cooler than integrated circuit development), how much physics and information theory is involved in it. Applications of telecommunication implementation spill over to other fields, e.g. some proposed quantum computing approaches are remarkably related to telecommunication technology, e.g. microwaves and silicon photonics.

This understanding made Ciro Santilli wish he had opted for telecommunication engineering when he was back in school in Brazil. For some incomprehensible reason, telecommunications was the least competitive specialization in the electric engineering department at the time, behind even power electronics. This goes to show both how completely unrelated to reality university is, and how completely outdated Brazil is/was. Sad stuff.

Very interesting story! A predecessor to microwave transmission for trading.

We are at a point in history where the electrical telegraph is well established.

But people don't want to press letters one by one on a switch. They want to talk!

The first phones appear to have used telegraph lines directly.

Also wired phones don't require modulation, which likely made their development much easier than wireless voice transmission. You just send the signal as a voltage differential directly obtained from the air pressure: how the telephone works.

This section is about telecommunication systems that are based on top of telephone lines.

Telephone lines were ubiquitous from early on, and many technologies used them to send data, including much after regular phone calls became obsolete with VoIP.

These market forces tended to eventually crush non-telephone-based systems such as telex. Maybe in that case it was just that the name sounded like a thing of the 50's. But still. Dead.

Not a telephone-based system, needing its own network, and was killed particularly by fax which is. Telex evolved from the Telegraph, which is a binary system at the physical layer.

Uses telephone lines, and therefore were still usable much much after the Internet made them obsolete, which is quite funny.

Modulation basically means encoding data on a carrier wave.

Image that we are at a point in history where spark-gap transmitters can send Morse code.

But now people want to send voice. How to do it?

It would not be practical without modulation: Why can't you send voice without modulation?

Basically, the antenna has to be very, very large, more comparable to wavelength. E.g. even for the higher pitches, we fall in very low frequency, so have a look at the size of some of the submarine VLF antennas! They are like football pitch sized.