Got it, though it wasn't meant as a dismissal...just surprise.

Although the beacon system (technically a form of semaphore) could likely have been much better optimized.

For example, if a single pyre went unattended or was otherwise unable to light their fire (for example say an orc band attacked it), the whole system would fail, and there would be no way of knowing that it had failed. Consider also the possibility that one of the teams may have been able to light their fire, but for fear of drawing enemy attention to themselves, choose not to. Same effect. A more failsafe option would be to have the fires constantly burning with the light being cut off as the signal bit. This could be accomplished quickly and easily by having some shutter that drops down and blocks the fire's light. If one of the stations were abandoned or damaged, its fire would go out, alerting the network that something was amiss. This also means that the cowards who don't want to alert orcs to their position need only stop tending their station when in danger, and they are free to flee.

Of course once you have some shutter in place to quickly block out light, you can presumably raise and lower the shutter. With an appropriate protocol, you can essentially achieve a visual telegraph. If each station maintains two fires, you can achieve bi-directional communication. This is also good for eliminating false positives for the main alert function if one fire just goes out for some reason.

It's interesting that real life semaphore systems like Phryctoria or the Byzantine Beacons did not implement fail-safe methods.

You don’t have to use a fictional example of a signal fire... it was used in ancient China to send exactly this message: “Send the army”

“In some safety-critical scenarios, such as concerning the integrity of reactor containments, and metal vaults and bulkheads in maritime structures, it can be important to minimise the number of penetrations made through such metal structures for communications cabling. The use of neutrons for information transmission through such structures could negate the need for such penetrations and is perhaps also relevant to scenarios where limited transmissions are desirable in difficult circumstances, such as for emergency rescue operations.”

There can be many innovative use cases in industry or military applications where wires cannot penetrate the surface of an object and other signals are too weak to penetrate the object to transmit data about something mission critical.

This warrants future investigation at the very least, however impractical it may be. Quantum computers may also benefit from this technology, etc.

Just because it doesn’t have any immediate applications right now doesn’t mean it won’t in the future.

You’re basically right.

Miners trapped in a cave not penetrated by E&M waves?

Wont work.

Signal from inside a reactor?

No. No logic can modulate the signal in said reactor that isn't destroyed by the radiation.

If you have a pneumatic arm to modulate this thing, use it to flip a magnet. That’ll better penetrate any shield than neutrons.

The first trans-atlantic telegraph message took 16 hours to send.

Probably military applications too if it evades conventional detection.

Space?

I believe the theoretical throughput of a modulated neutrons is very very high - substantially higher than the electromagnetic waves we send today.

Given that, perhaps the people of 1000 years from now will be using them to do data transfer because electromagnetic waves are far too primitive and low bandwidth.