Because I like technological development being gonzo, what if it starts with the ability to send words on enchanted paper.
So the fist step was you have a way to enchant two pieces of paper, so anything written on one appears on the other through the law of similarity.
Post offices are created. In the post office, echo-papers from the posts up and down the line are checked, and scribes transcribe it to papers for the next step on the line. Couriers carry the echo-papers of adjacent stops to each other, refreshing the ability to communicate.
Long distance expensive echo-papers are also distributed, and those are checked more often for messages, providing expensive express service.
This is also used in war. Attacking the scribes of communication becomes key to disrupting the enemy's ability to coordinate. Even better is suborning them, or getting ahold of an echo paper and being able to intercept messages.
Spies work out how to duplicate one of these echo-papers and intercept the enemy communications. After this causes a tactical upset, it also opens up the world for the newspaper. One primary paper and a bunch of echo-papers.
So one piece of paper, when written on, makes things appear on many other pieces of paper.
Thus the echopaper news is born.
The ratio -- between primary and secondary -- is bounded. And the number of times the master can be erased is as well. So you have to buy new newspapers every week or so.
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Technological advancement automates this, with enchanted quills copying from one piece of paper to another to allow for larger networks and causing an employment crisis among scribes. You still need scribes to start the communication, and deliver it, because who knows how to read and write? But the large number of scribes that run the echo-channels are rendered unemployed as the magic quills take over.
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To get radio, take a strip of paper, a continual light spell, and a magic mouth, and put it in a box. The mouth is told to read the paper and say what is sees. The broadcasters scribes write on their piece of paper, and the mouth-boxes repeat what they hear.
The voice of the broadcaster is thus always that of the magic mouth enchantment, which lets the DM use a funny voice.
The paper inside the mouth-box is a long strip on a spool. The mouth-box has a crank on the side that advances the strip. As the broadcasting paper runs out of ability to be reused, listeners have to turn the crank to the next setting to get signals.
Advanced mouthboxes even have the ability to change which spool they are using, after which you need to tune in to the current broadcast mark.
Humidity can stretch the paper, causing letters to be garbled or dropped, as can damage to the strip or misturning the crank.
The mouth sometimes also misreads words. New alphabets are developed to clean this up.
Over time, the language used to instruct the magic mouths on what to say drifts away from being readable/written by humans to ones more suitable for the mouth and make more efficient use of paper. Mouths that know musical notation are even developed.
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The automated quill technology is also warped beyond recognition. Careful use of symbols and connecting the "quill" up to devices allows echo-paper to be used to get large numbers of quills to be controlled by one set of instructions.
Using this technique, one master scribe-weaver can run 100s of looms at once. Mechanics run between the looms, repairing things that go wrong, and replacing spools of echo-paper as they run out.
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The first quillion "warrior" was a toy. The next dozen where playing pieces that the sun king used to play a board game.
But over time they became cheaper and more dexterious. An army of quillions marched on the kingdom, followed by warrior-scribes whose ink-stained hands dripped with the blood of their foes.
As the kingdom fell, the knights turned to each other in despair. Finally, it had happened. The pen had proved mightier than the sword.