The basement of Kaichi's residence.

Yang Xi looked at the rune diaphragm carved out by Jia Yi to make and receive sounds, and hesitated: "Jia Yi, is your voice code reliable?"

"Of course, there is no problem, even if the encoding is not successful, the sound will not change, and it can still be received. Jia Yi said very firmly.

Because the underwater environment is noisy, the water current, animals and plants will emit all kinds of noise, which will also be received by the sonar detector, resulting in a slightly farther distance, the received sound is not very clear, and it is not easy to distinguish with the environmental noise.

Therefore, Jiayi encoded the sound, that is, the frequency amplitude of the sound conformed to a certain specification, such as three high and one low, and then high and low, etc., after receiving the sound, it was also verified according to this rule, if it did not meet the coding rules, then it was noise and discarded. Of course, the real coding rules are of course not so simple, Jiayi recalled the Morse code book he saw in junior high school, and chose the Morse code of his name as the code, and the high and low interval of the sound frequency of the sonar as the distinction between 0 and 1.

When Jiayi took the high school entrance examination in his last life, his name on the volunteer card was painted out with Chinese characters, and he was also issued a codebook at that time, so that he could find his corresponding name, but fortunately, because of his interest, he turned over the entire codebook.

Jia Yi translated, it is 0857 0001.

Although the sound can be encoded, but there are limitations, the sound speed of this world is no different from that on the earth, it is almost 340m/s in the air (this assumes that a second in the other world is the same length as on the earth), the underwater speed is 1500 meters per second, assuming that the frequency of the sound wave used is 35KHZ, then the wavelength of the ultrasonic wave is about 4.3 cm.

Jiayi is translated into two Chinese characters, each Chinese character is represented by a four-digit numeric code, and each number is translated into a Morse code of five digits, then the two Chinese characters are 40-digit Morse code, expressed by sound waves, even if a wavelength represents a Morse code, the total length of the wavelength is about 1.7 meters.

However, this calculation is meaningless, because if the frequency of the sound wave is fixed, the longer the wavelength, the faster the speed, and the transmission time will not change. In fact, the amount of information stored is only related to speed, because in the same medium, only the speed is constant, and the wavelength and frequency are inversely proportional.

Jia Yi thought about it for a long time, only to realize that what he was thinking about was useless, he didn't have the idea of developing a telegram for the time being, although the basis of the telegram had appeared, and there was a legendary mage who was proficient in electromagnetic spells, and related electromagnetic wave spells had also been developed, but they were all relatively high-end. Jiayi is still laying a solid foundation, and it is still not enough to develop electromagnetic waves.

Throwing away the manuscript paper in his hand, Jia Yi continued to carve his magic circle, the idea of coding is still right, but it is not as easy to implement as imagined, and Jia Yi's ideal idea of carrying a Morse code per wavelength is still too idealistic. Because the time of one wavelength is only one thirty-fifteenth of a second, Jiayi's magic circle cannot reach this accuracy at present.

He now, even if he is controlled by the magic circle, he can distinguish 20 syllables per second, that is, it takes 2 seconds to transmit the complete Morse code of one or two characters of Jiayi, and every time Jiayi probes, from the beginning to the end, in order to parse the code, it takes 4 seconds, and the time spent in the process of sound transmission has not been calculated.

If it's three kilometers, it's a total of 6 seconds. This time is too long, if the speed of the monster is fast enough, it may hit your eyes.

Yang Xi looked at the manuscript paper that Jia Yi put down, it was very strange, he calculated the frequency, wavelength, and drew a little horizontal and horizontal, with numbers, and wrote the numbers 0857 0001, and then threw it aside to calculate the time, and he was a little confused.

"Kaichi, what are you counting?

Jia Yi said that he had a problem with the code, and he thought it took too long, and the 8-digit number took two seconds, but he didn't say why he chose the 8-digit number as the code.

Yang Xi raised the manuscript paper in his hand: "That's it, wouldn't it be good if you reduced a few digits, why do you have to choose 8 digits, just choose 4 digits, no matter what, two can do it." ”

Jia Yi suddenly,He was a little too stubborn about some things in his previous life.,Almost couldn't turn the corner.,And it's also a kind of lazy thinking.,If you want to code.,You don't need to follow the Morse code exactly.,Isn't it good to come directly to binary.。 Originally, Morse code is binary, and it is represented by ticking.

But 8 digits are too long, even if the binary is not the first 0 has 24 bits, in the end, he chose 857 three numbers, converted into binary only 10 bits, just half a second, back and forth encoding analysis just one second, almost enough, if it is simple, the anti-interference ability is weakened a lot.

After discussing with Yangxi, Jia Yi made a plan, but Chester, who was on the side, was a little dumbfounded: "Jia Yi, every time you make magic props, is it so troublesome? It's such a complicated thing." ”

In fact, these things are not too complicated, and Chester can still understand them when he talks about them carefully, but at first glance, they seem complicated, and Chester does seem to lack a little talent in pure theory and mathematics.

"Sharpening knives is not a mistake for woodcutters. This proverb can be used in any world, even if there is no proverb, it can be understood literally.

The preparations have been made, and they have stepped up their time to start making it, and Kaichi has spent a lot of time in order to calculate the above data. Although it is said that sharpening knives does not mistake woodcutters, but Jiayi sometimes sharpens not only the knife, but also the unusable saw.

By the time they got back to the dormitory in the evening, they hadn't even made a finished product, but all their preparations were done, and as long as there were no problems with the first product, the rest would be fast.

The next day there were no problems, and the next day, they made the first sonar detector that was experimental, and although there was a delay of one second, the detection accuracy and distance were better than the original old version.

At this point, they could say that although the power of their sonar detector and the level of the magic array may not be as advantageous as that of the academy, the use of coding methods to resist interference is not much worse than that of the academy. Because of the speed of sound transmission, on the ground, the sonar performance is not as good as in the water, because the speed in the water is faster and the detection is more timely.

When Jiayi and the others were busy taking time to make the sonar detector, the notice of the academy on "Exploring Lake Taberina and Cleaning up the Dangerous Factors Around the Academy" also officially came out.

The academy has officially announced that all academy students will participate in this operation, and will also recruit some non-academy mages within the academy to form a real mage army and march into Lake Taberina in full swing. The Academy does not prohibit the rest of the population from following, but it is not allowed to influence the actions of the Academy, and the safety of non-regular personnel is not guaranteed.

The recruited non-academy mages are actively invited by the academy, and of course, they can also take the initiative to sign up and receive the academy's assessment. All of them will be grouped according to the ratio of high and low strength, and will be allotted standard equipment to ensure the safety of each member.

But how exactly it is grouped and what equipment is not stated in the notice.

As Jia Yi expected, the time was set after the Meng Spring Festival, on the seventh day after the Meng Spring Festival, the penultimate day of their traditional period.

Jia Yi calculated very clearly when the traditional trials of the academy would end, and a day would not be bad, and he would count the days every day, and another day would pass, and the traditional trials would be one day less. Of course, he could actually look at the calendar, and by the first day of March, their academy tradition was over.

Although the traditional period of admission to the college has been going on for a long time, it doesn't even have an official name, and I don't know if it's because of laziness or what.