Even with Jin absent, the members of the Jin Family decided to hold a brainstorming session to figure out how to put the flashing communicator to practical use.
They planned to dive into it in earnest the next morning, on the 19th, right after breakfast.
"First, why don't we list the inconvenient points and think about how to fix them?"
Everyone nodded in agreement with Hanna's suggestion.
"Sounds good to me."
"All right, then I'll start with the flaws. First, the communication range is too short. It's useless if you can't see it with your own eyes. On top of that, the amount of information you can send is really small."
At this point, Lishia raised a hand to ask a question.
"Excuse me, Hanna-chan. What exactly do you mean by 'the amount of information you can send'?"
"Um, how should I put it... You see, the current method works by changing the number and interval of flashes, assigning meanings to those patterns, and matching them against a reference table."
One might call it a primitive form of Morse code, or perhaps an extension of semaphore signaling.
"Ah, I see. That makes sense....Please go on."
"Okay....Are there any other drawbacks?"
"Hmm, let's see..."
"Oh, and set aside things like costs or manufacturing difficulties for now."
Everyone tilted their heads in thought, but no other flaws immediately came to mind beyond what Hanna had pointed out.
"Then let's think about ways to eliminate those flaws!"
"...Aren't communication range and visibility essentially tied together?" Beena remarked. "The simplest answer would be to crank up the brightness, right?"
"Yeah, I think Beena-oneechan is right. But if we do that, the glare will be as blinding as a searchlight... Oh, wait! How about using infrared?"
"Hanna-chan, the human eye can't see infrared, can it?" Saki pointed out, but Hanna maintained a serene smile.
"Right. So how about we use a magi-device like a golem's eye for the receiver, and have it blink a visible light lamp based on the data it picks up?"
"That could be quite interesting. As expected of Hanna-chan," Reinhard remarked, clearly impressed.
"Ah, if we're going to use a magi-device anyway, instead of making a lamp blink, why not have it decode the signal directly?" suggested Milowina, who had been listening quietly until now.
"...That's a great idea!"
"Yes, exactly that!"
Hanna and Beena were the first to chime in with enthusiastic agreement.
"Oh? Sounds like a lively debate."
"Onii-chan?!"
"Jin-nii?!"
To everyone's surprise, Jin walked into the room.
"Sion and the others seemed completely swamped attending to the foreign dignitaries, so I only stayed for one night before heading back."
Seeing how exhausting it was for them to entertain guests from abroad, Jin explained that he had taken his leave early.
"So, are you brainstorming magi-communicators?"
"We are! Will you tell us what you think, Onii-chan?"
Hanna brought Jin up to speed on everything they had discussed so far.
"...I see. So flashing communicators fell out of favor, huh?"
Jin felt a twinge of regret.
If the technology had continued to evolve, the kind of magi-communicator Hanna and the others were envisioning might already be a reality today.
"Using infrared is definitely a great idea," Jin agreed. "Infrared can easily cut through light fog, too."
Ideally, Jin would have preferred to use radio waves, but he had no idea how to actually transmit them.
He knew the basic principle: radio waves are generated whenever a spark snaps.
In the real world, that phenomenon was loathed as "noise."
Whenever a mechanical power switch near a PC or audio equipment was flipped on or off—especially off—it often introduced static. In those moments, radio waves were being emitted... or so he understood.
"...Wait, Onii-chan, the magi-screen and magic eye communicate using mana waves, right?" Hanna asked with innocent curiosity. "Why is it that we can use mana waves, but not radio waves?"
"Well, strictly speaking, it's not that we can't use them so much as we've chosen not to."
"Huh? What do you mean?"
"Mana waves are simply far more convenient to work with than radio waves, and you barely have to worry about interference. Radio waves, on the other hand..."
Jin explained that, having seen the complications back in modern Japan—scrambles over frequency bands, electronic devices malfunctioning from interference, public uproar over potential health hazards—he had deliberately leaned toward a magic-based approach.
"If we apply high voltage at a high frequency to a transmission antenna, I suspect radio waves would propagate just fine."
With that method, he believed basic AM (Amplitude Modulation) broadcasts might be achievable, but he didn't know how to build the necessary electronic circuitry.
"Yeah, that's true. I wouldn't know where to start with electronic circuits either," Hanna admitted.
Without any reference materials to go on, even someone of Hanna's intellect couldn't build them out of thin air.
That was when Elsa voiced an idea of her own.
"Jin-nii, isn't light just a type of electromagnetic wave?"
"...Ah!"
Elsa's offhand remark struck Jin like a bolt of lightning.
"You're completely right! In that case, if I modify the Light spell..."
The fundamental difference between radio waves and light was merely their wavelength.
Wavelengths longer than far-infrared fell into submillimeter waves, millimeter waves, microwaves, and so forth.
Wavelengths in those bands traveled in straight paths and bounced off objects, which was why they were used in radar.
Setting that aside for a moment, Jin realized that if he could emit far-infrared, with a bit more tinkering, he could likely generate microwaves and VHF waves as well. He immediately set to work analyzing the concept.
"Hmm... If I rewrite this part of the magi-formula and tweak these parameters here... this actually looks doable."
As his train of thought progressed, the structure of the magi-formula suddenly felt strikingly familiar.
"Wait... Is this the Induction Radiator?"
The Induction Radiator was a weapon that generated heat by using Induction to produce eddy currents in target metals.
"That relied on a magnetic field, whereas this uses an electric field. No wonder they're so similar."
Jin chided himself for not realizing the connection sooner.
"I think transmission is well within our reach."
Jin figured he could leave modulation to a magi-brain, which would essentially act as the CPU.
"The real hurdle will be reception."
"Yeah, that definitely sounds tough..."
At that moment, Mine—who usually stayed quiet during technical discussions to serve everyone tea and refreshments—spoke up uncharacteristically.
"Um, there is just one thing I do not quite understand. May I ask a question?"
"Of course. What is it, Mother-in-law?"
"Thank you....Well, I was wondering, since we already have the manacam as a means of communication, why aren't we simply using that?"
It was an entirely valid question. Between the manacam used by those affiliated with Hourai Island and the manaphone accessible throughout ordinary nations, why not rely on or adapt existing systems?
"Ah, I see why you'd ask. You see, the manacam is a magi-device that communicates using mana waves. What we're trying to design right now is a magi-device that communicates using radio waves."
"I see... So you are trying to use something fundamentally different from mana waves."
It seemed she had grasped the general distinction.
"Besides, part of the reason we're all brainstorming this is simply because figuring these things out is fun."
"Yes, Haha-sama. Everyone here just loves brainstorming ideas, talking them through, and bringing them to life."
With Elsa's supplementary explanation, Mine finally nodded, thoroughly satisfied.