Chapter 631 PCM
It's unrealistic to want to make it as big as the Citigroups. They don't even have food to eat. Other troops are not doing well either, right?

However, with the total production of several hundred V-5s, concentrating a small portion to create a small air assault force would have practical significance and could also help explore the tactical use of helicopters.

"The armed and transport versions of the V-5 can be mixed and used in the same unit, with one part responsible for transportation and the other for air fire support. The armed version can be equipped with the Type 61 individual anti-tank missile and can also be used to decapitate enemy tanks."

Gao Zhendong added that he did not act rashly and said that he wanted to develop air assault and airborne troops, but only slightly expanded the armed capabilities.

This time, the army leaders fell into deep thought and had to think about this matter carefully.

After a long moment, he nodded and said, "Well, we can explore it. We can't do too much with this thing, but we can focus on it and study new tactics to increase the rapid support capabilities for the comrades on border patrol."

This matter does not involve new equipment. The Air Force is already working on the armed version of the V-5. The two sides can work together to integrate the anti-tank capability.

As for whether the V-5 can go to the plateau, Gao Zhendong doesn't know, but he knows a little-known fact: the practical ceiling data of the V-5 is slightly higher than that of the UH-60 Black Hawk of the Americans, so it should still be of some use.

Moreover, even if we can't get up, it's not a big deal. The plains and mountains can also play a role. There is more than just snowy plateaus on the border.

With this mechanism, when the Russians deliberately ambushed and retaliated against our comrades in 69 because they suffered a loss, we probably would not have suffered such a severe loss, and even the war correspondents would not have been sacrificed.

As for the fact that the Russians should have had Arrow-2 portable air defense missiles at that time, hehe, they installed infrared jamming bombs. That thing is cheap, and the effectiveness of Arrow-2 when facing infrared jamming bombs is not very good.

The army leader turned around and said to the comrades around him: "Please remember this matter and push it forward later."

Gao Zhendong only mentioned the use of helicopters briefly, and the following matters had nothing to do with him. The comrades in charge of these matters in the army were much more skilled than him in these professional matters.

Turning back, the army leader said: "Next, we will organize personnel to summarize the use of protective carrying gear, helmets, bulletproof plates and other new equipment, and feedback the experience and requirements as soon as possible, so as to end the trial period as soon as possible and enter the formal equipment period."

At least let the helmets and protective carrying gear be pushed out. The bulletproof plates are a bit expensive, so let's implement it step by step. Important units should be equipped with them first, or they should be stored. Except for a small number of front-line and patrol teams, whoever goes to the battlefield can use them.

Anyway, there is no such thing as training for the use of bulletproof inserts. Just insert them and fasten them. If you are really worried, you can try putting an iron plate in your pocket to feel it first.

Fortunately, compared with aramid and other fiber bulletproof vests, bulletproof inserts have a much longer shelf life and can be accumulated slowly.

After that, he asked Gao Zhendong with some doubt: "Why does this helmet you guys made look familiar to me?"

As a senior general, he had naturally seen a lot of things. This helmet without the cover looked familiar, but it was definitely not the one the Japanese soldiers wore.

Gao Zhendong said openly, "This thing is copied. We have done research and found that the East Hans M56 has the best performance and meets all our requirements. So we just copied it directly. This way it is faster. It doesn't matter if it's embarrassing or not. What's important is that our comrades can use it sooner."

After hearing his words, the leaders of the National Defense Committee and the Army couldn't help laughing, saying, "It's not shameful, it's not shameful, as long as this kind of thing is useful, it doesn't matter where it came from."

East Hans' M56 is the best helmet in terms of overall performance. Interestingly, it is said that this thing was developed in S2, but someone thought it was not good-looking enough and did not equip it.

The soldiers also laughed. No matter where this thing came from, its protective performance was not directly demonstrated, but the protective area was visibly good, even the back of the neck was taken into consideration. It was also easy to use and had many uses.

This time, they experienced in person the simple process of a seminar and equipment demonstration, and truly felt how their comrades in the rear worked hard for them.
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Two groups of people came to the reception room of the Third Factory, gathered together, and waited for Gao Zhendong.

They were from the Military Communications Institute and the Communications Academy respectively. The former was the comrade who had recently consulted Gao Zhendong about military communications equipment, and the latter was working on a program-controlled space-separation switching system.

They came here at the call of Gao Zhendong, who was going to help them solve the problem of converting voice to digital.

For the former, it solved the problem of the digital radio station they were working on, and for the latter, it was a reserve of knowledge. After all, what they are working on now is still the space division switch, and the digital switch has not yet started.

The two parties greeted each other in a friendly manner, but tacitly did not ask each other about their backgrounds and work.

After waiting for a while, Gao Zhendong came in.

"Is everyone here? Sit down." After Gao Zhendong put down the stack of information in his hand and counted the number of people, he asked everyone to sit down.

"One, two... seven. Well, it seems that the information is enough. Come on, one copy for each person."

Several people hurriedly took the materials from Gao Zhendong.

This material is the basic principle of pulse code modulation (PCM).

As everyone opened the book, Gao Zhendong smiled and said, "Today, let's put aside the analog-to-digital (AD) and digital-to-analog (DA) conversions. Assuming that we already have sufficient analog-to-digital conversion capabilities, how can we use this capability to convert voice signals into digital signals?"

If we were to talk about AD and DA as well, there would be too much to say and it would be unnecessary. They each have their own ways and cannot be brought together to talk about them.

All comrades are aware of this truth. Moreover, in voice communications, since the speed and bandwidth requirements are not high, the AD/DA technology itself is not a problem that bothers them. How to make good use of AD/DA is their problem.

Seeing that everyone understood what he meant, Gao Zhendong went straight to the point.

"Pulse code modulation is divided into three stages: sampling, quantization and encoding. As for sampling, I think everyone knows it, so I won't say more. Just read the materials."

To put it simply, sampling is to use a sampler to collect the instantaneous voltage of the signal. This is the most basic thing, and everyone here understands it.

"What do you want to ask about quantification?" Gao Zhendong did not read the materials one by one. They were all veterans. That method was not only tiring, but also might not be effective.

"Chief Engineer Gao, since we have already taken samples, we have obtained a clear value. We can just use this value to record the voltage value. Why do we need to quantify it?"

Gao Zhendong smiled and said, "In order to save data capacity, the sampled value is still a value with infinite possibilities. Using a limited number to store it is very resource-consuming, even if the valid digits are limited. For example, 1.567 will cause two problems."

Gao Zhendong turned around and wrote a few words on the blackboard: "First, to accurately detect this value, a complex circuit is needed. Second, the encoding and storage of this value are very space-consuming. I think everyone is familiar with the storage of floating-point numbers. But for voice signals, it is not necessary to be so precise. As long as the instantaneous voltage of the signal reaches a certain accuracy range, it can guarantee understandable reproduction, so this is actually a waste of resources."

"Oh, I understand. In this way, we only need to divide the signal amplitude from 0 to the maximum into certain levels according to the range, such as 8 levels. Below 0.5 is 0, 0.5 to 1.5 is 1, and so on. Above 6.5 is 7. From 0 to 7, the entire amplitude range of the signal's instantaneous voltage can be covered. In this way, a three-digit binary number can ensure better reproduction of speech! And it saves a lot of space!" Everyone present was an elite and understood it immediately.

"Not only that, this way, the detection circuit will also be very simple. It does not require too precise values. By using a comparison circuit with certain values, the signal code can be encoded!" Another person also reacted very quickly.

It’s easy to talk to someone who understands. Gao Zhendong smiled and said, “Yes, that’s what I mean… As for encoding, it’s to use binary numbers to record the quantized results.”

After that, Gao Zhendong systematically went over the knowledge related to quantization and coding.

Gao Zhendong spoke quickly, but everyone could understand him. This step is actually very simple in principle.

After finishing speaking, Gao Zhendong smiled and said, "Comrades, isn't it very simple?"

Everyone laughed. This is really a matter of those who don't know how to do it, but it's not difficult for those who do. In fact, at this point, even if Gao Zhendong didn't say it, they probably understood it themselves, but they just haven't organized themselves into a systematic way yet.

"Well, okay, now that we have explained it briefly, let's talk about something that is not so simple. The uniformly quantized signal-to-noise ratio..."

The inaccuracy of quantification will definitely bring in noise. What Gao Zhendong is talking to them about now is how to minimize the impact of this noise.

From here on, some mathematical formulas appear. For some of the content, Gao Zhendong directly uses the results, but the source is not explained, otherwise it would be too long.

Several comrades were able to keep up. In fact, in applied science, a lot of knowledge only cares about the results, regardless of the source. Even if it is just a hypothesis, it can be used effectively.

"…So we can calculate that for every additional bit of binary code length, the signal-to-noise ratio increases by 6dB. In other words, if you want to reduce quantization noise, you need to increase the code length of the encoding."

Everyone understands this. Even if this space-saving encoding method is used, a certain price must be paid to ensure the quality of the call. However, they don't know how much the price will be yet.

(End of this chapter)