Chapter 413: Let’s do air separation
For the comrades of the Institute of Communications, they were suddenly confused. Chief Engineer Gao, does the program-controlled switch still have so much work?
It’s outrageous to come up with one type of switch yourself, and then you have three types of switches at once.
If they can still have a rough understanding of air division switches, then space switches and digital switches are completely beyond their scope of knowledge for the time being.
But don’t just ask, you have to tell me what these three types of switches are and what are the differences.
Gao Zhendong then introduced the basic principles, advantages and disadvantages of these three types of switches. Several comrades from the Telephone Office of the Institute of Communications immediately fell in love with digital switches at first sight. I want this!
But as the chief engineer of the Communications Institute, Mr. Feng fell into deep thought.
Ordinary employees only need to be technologically advanced and have a sense of accomplishment, but as the chief engineer of the Communications Institute, he has many things to consider.
"General Engineer Gao, first of all exclude the time division switch. This thing is neither good nor bad. The basic technical difficulty is about the same as the numbers, but in terms of advantages, it always feels a little inferior."
Feng The general choice is also the choice of most people. If you don't know about digital switches, that's it. After knowing it, the long-lasting option of time and division will be eliminated first.
Gao Zhendong nodded: "Well, Mr. Feng's judgment is basically correct. Time-division switches are originally the basic technology of digital switches."
Other countries in the world that mainly research and produce program-controlled switches also invariably use time-division switches. The exchange step didn't last too long.
Mr. Feng was very confused about the remaining two types. One is simple, low in difficulty and easy to produce results, and the other is extremely advanced in one step. The world's first practical digital switch was originally built in 10 It was made by Gallic Chicken after 20 years.
After much deliberation, he found it difficult to make up his mind, so he simply asked his master to make the decision.
"General Engineer Gao, what is your opinion?"
Gao Zhendong smiled and said: "Air separation exchange!"
Seeing that everyone was a little confused, he explained the reason to everyone.
“First of all, air separation exchange and current artificial exchange are very consistent in principle. All required environmental conditions can basically remain unchanged and the transition is smooth.”
Time division and Digital switching has higher requirements for line quality. Essentially, these two technologies put more data on the same line. When other conditions are the same, Boss Shannon said that the higher the speed, the shorter the distance.
Smooth transition and no network transformation is very important to us now. Transformation costs money.
Mr. Feng nodded. Mr. Gao was indeed thoughtful and not just technical. He fully considered all aspects of the situation before making a decision.
What Gao Zhendong just said is the point that Mr. Feng has considered the most and is the most difficult to give up. He also understands Shannon's theorem. Although Shannon lived until 2001, "Communication under Noise" "But it was published in 1949, when Shannon was 33 years old.
“Secondly, the cost of digital switches is too high now.”
For the modulation technology of digital switches, Gao Zhendong is ready to adopt the most widely used PCM in one step. , now that integrated circuits have not grown up, both ends of the call need to perform an A/D (analog-to-digital) and a D/A (digital-to-analog) conversion, and the circuit cost is very high.
Moreover, in addition to the cost of this part of the circuit, digital switches require more memory, which further pushes up the cost of digital switches.
No one was as familiar with this area as Gao Zhendong. When Gao Zhendong talked about it, they realized that there was such a thing.
However, Mr. Feng still raised his concerns: "Mr. Gao, if the switch from program-controlled air separation switches to universal program-controlled digital switches in the future will cause the original air separation switches to be idle and wasted? "
Gao Zhendong shook his head: "No, as long as conversion equipment is added to the air division switch, it can be easily integrated into the digital switching network."
Take the first one in 1970. For the first Gallic chicken who came up with digital switches, his plan in 1981 was to connect 1/3 of the users to digital switches in 1983, and to realize all digital switches from 1990 to 1992.
Before this, a mixed network of air division switches and digital switches was also used.
Even Gallic Chicken, which was once so brilliant in telecommunications equipment, took such a long process to achieve full digitalization, let alone us now. Advanced is not necessarily important, but suitability is important.
But perhaps even the Gallic Chickens themselves could not have imagined that their brilliant telecommunications industry was finally sold out.
After listening to Gao Zhendong’s analysis, Chief Engineer Feng also made up his mind.
"Mr. Gao, let's build a program-controlled air division switch first."
In the original time and space, between the 1960s and 1970s, we had a period of high ambitions, blindly disregarding the actual technical foundation, There is a history of pursuing technological advancement, irrationally raising parameter requirements, and forcibly launching projects.
In the end, the results are mostly not very good. Money is spent, time is wasted, and the results are basically very few.
Gao Zhendong is very aware of this, so naturally he should try to avoid this situation within the scope of his control.
Gao Zhendong nodded: "Well, okay, let's decide first and tend to do this."
Now that the direction has been decided, what can be done has also been decided. . "Mr. Feng, before you come back with further status data, we can do three things first."
Mr. Feng picked up his pen and said, "Mr. Gao, please tell me."
"The first thing is to determine whether we have a suitable residual spring relay. If not, can we copy it? If we can't even copy it, No, is there a suitable ordinary relay? ”
The residual reed relay is a state-maintaining relay. Its characteristic is that it can use residual magnetism to maintain the working state without the need for continuous power supply. To put it bluntly, it saves electricity.
Although a single relay does not seem to have much power, large-scale switches require tens of thousands of relays, which together consume a lot of power.
This is the choice of Citigroup in the air separation switch. The Citigroup these days is still trustworthy and is not in the state of writing PPT randomly.
Like other major switch manufacturing countries, Xiaojiaizi has solved this problem, but they have taken a different approach, mechanically maintaining it, and Xiaojiaizi's brain circuit is always different.
Whether there are any remaining reed relays, Mr. Feng doesn’t know yet. He writes this down.
There is a comrade from the Telephone Research Institute who knows something about other relays: "General Engineer Gao, we have copied the РПН flat relay, right?"
That's Lao Maozi. That thing in the 47-type telephone exchange. The size and weight of this thing made Gao Zhendong feel a little uncomfortable: "That one is a bit too big, let's use it as a last choice."
I didn't reject it outright, it was considered Save some face.
Mr. Feng also laughed when he thought about the РПН that could kill people. He understood what Gao Zhendong meant.
“The second thing is an imitation telephone, which is a dial telephone with a dial. The dial generates pulses with a duty cycle of 1.3/1 and a maximum pulse frequency of 20Hz.”
< br>Dial-up telephones with dial dials were still high-end products in our country until the 1980s. Most units had hand-crank telephones. In fact, it was not the high-end telephones, but a problem with the switch.
This kind of dial itself is actually a pulse generating device. When the dial is turned, the dial will automatically generate a corresponding number of pulses based on the rotation distance of the numbers. The number "1" is one pulse. " 2" is two, and so on.
This is also the reason why old dial phones have 0 at the end, "0" is 10 pulses!
As for why Gao Zhendong doesn't just make touch-tone phones, the problem is still the same. Buttons are expensive! The circuit that uses the buttons to generate a corresponding number of pulses is much more expensive than the dial these days.
As for the DTMF (Dual Tone Multi-Frequency) signal actually used by touch-tone phones, don’t even think about it. Two frequency signals are used to represent numbers. As soon as you hear the name, you will know that in this day and age, it can be compared to one second. 20 pulses is much more troublesome.
Anyway, this thing is easy to copy. Even if Gao Zhendong’s requirements are not necessarily the same as the prototype, it is not difficult to modify it.
The comrades in the Institute of Communications are full of confidence. I am familiar with this thing!
“Thirdly, I will share with you some of my thoughts on program-controlled switches during this period. Please go back and take a look and give me your opinions.”
Look, Chief Engineer Gao is too humble and "gives advice."
The comrades at the Telephone Research Institute were very excited about this unexpected gain. Judging from what Chief Engineer Gao just said, these research results must be of great benefit to them.
Even Chief Engineer Feng is very interested in this. He participated in the imitation of Type 47 and knows what the structure, components and installation of Type 47 are like.
But why is this structure adopted? Why are rotary selectors, lifting selectors combined with relays? Why are so many of these devices used instead of more or less? To be honest, they really don’t Why is it so clear, or the understanding is not systematic and thorough enough?
In short, the theoretical foundation is weak. This sentence has been put aside for decades, and there is still nothing wrong with it.
Gao Zhendong walked around the safe for a long time, then walked back and handed a stack of manuscripts to Chief Engineer Feng.
The comrades from the Institute of Communications looked at Gao Zhendong’s safe with hot eyes. What other good things are in it?
But they also know that whoever dares to dream of this safe will have a secure life for the rest of his life.
Actually, there is nothing important in this safe, it is just a scapegoat.
Chief Engineer Feng quickly took it over and had a sneak peek.
The manuscript was not thick, about thirty or forty pages long, and the content seemed very simple, but it made Chief Engineer Feng very jealous.
The basic composition and functions of the switching system, basic knowledge of traffic, voice channel network structure, control method, and signal method.
They are all basic knowledge, but they are all theoretical, which happens to be missing. That's theory.
(End of this chapter)