Reborn Tech Maniac

Chapter 119 Switches and Modems

In the field of network operations in the telecommunications industry, monopoly is relatively common. Take the United States as an example. AT&T, the American Telephone and Telegraph Company, occupies 80% of the US telephone market.

In 1984 in the previous life, AT&T was forced to split due to the antitrust lawsuit of the US Department of Justice.

Among them, there is a saying that before AT&T was split, IBM was the second largest company in the United States.After AT&T was split into seven companies, IBM's ranking became eighth.

This shows how far the monopoly phenomenon has reached at that time.

The field of equipment manufacturing in the telecommunications industry is also full of tycoons, with varying degrees of shadow of state capital.

Of course, it is not impossible for latecomers to join them now, because the world's telecommunications industry is ushering in a new round of technological upgrades.

The Public Switched Telephone Network (PSTN) is the largest network in the world, and its establishment date can be counted from Bell's invention of the telephone in 1876.

Among the two major components of the PSTN, the transmission system is mainly composed of transmission equipment and cables.

At present, the technology of transmission equipment is mainly based on carrier multiplexing, and the cable is mainly copper wire, but the corresponding latest technology, Synchronous Digital Hierarchy, that is, SDH and optical fiber, has gradually begun to emerge.

Another major component of the PSTN is the switching system, and the equipment used is mainly a telephone switchboard.

With the advancement of electronic technology, telephone exchanges have gone through magnet, step-by-step, and vertical-horizontal systems, and have developed to the current stage of program-controlled exchanges.

In 1970, France launched the world's first program-controlled digital telephone exchange, which adopted time-division multiplexing technology and large-scale integrated circuits.

Afterwards, other countries vigorously developed and quickly followed up.

In the previous life, the 1980s was the period when program-controlled digital telephone exchanges began to become popular in the world.

In the PSTN, the switch that the user connects through the direct connection is called the end office.

At present, analog signals are mainly used for transmission between users and end offices, and a system that completely uses digital signals to connect users and end offices—Integrated Services Digital Network, or ISDN, has emerged. For example, Deutsche Post decided in 1979 to All local telephone calls are digitized.

In the original time and space, after the 1990s, European countries represented by Germany and RB in Asia, ISDN was popularized on a large scale, but in the United States, because of poor marketing and little advantage in price, ISDN became tasteless.

As for China, although the telecommunications industry is developing rapidly, it needs a process after all.

Therefore, when ISDN was very common in European and American countries, China introduced this technology and began to install central office equipment in a few pilot cities.

But at this time, using Digital Subscriber Line Digital Subscriber Line or DSL technology, asymmetric Digital Subscriber Line Asymmetric Digital Subscriber Line or ADSL technology has matured and been promoted to the market.

So invisibly, China avoided the big pit of ISDN and directly entered the era of ADSL.

At the beginning of the telephone system design, it was mainly used to transmit voice calls. For economic considerations, the designed transmission frequency range was 300Hz to 3.4KHz.

The copper cable from the end office to the user can actually provide higher bandwidth, at least from the lowest frequency to 200-800KHz, depending on the circuit quality and the complexity of the equipment.

Unlike ISDN, which is a completely digital connection, DSL transmits data by using the additional frequency band higher than 3.4KHz on the telephone line, so that, like ISDN, it can provide various additional data services in addition to the basic telephone function.

The idea of ​​DSL can be traced back to Bell Labs in 1988. At that time, an engineer designed a method that could allow digital signals to be loaded into unused frequency bands of telephone lines, so that it could be used without affecting voice services. Data communications are provided over telephone lines.

However, Bell's management was not enthusiastic about the technology, because it would bring more profit if users installed two lines.

Bell woke up in the late 1990s when cable companies began offering broadband Internet access using two-way coax in their cable networks.

Realizing that most customers would absolutely forego installing two phone lines to access the Internet, Bell finally moved out of DSL technology, which they had been discussing for 10 years, to compete for broadband market share from cable network companies.

For a long time, DSL technology and cable modem CableModem, or CM, have become the main competitors in the home broadband access service market in Europe and North America.

As a reborn person, the development trend of the telecommunications industry in the next few decades is naturally within Tang Huan's grasp.

Although the threshold in this field is very high, the rapid advancement of technology also means changes in the rules. In the future, cable TV companies will use their own networks to challenge the status of traditional telecom companies to provide Internet access services. There are countless such examples.

The breakthrough that Tang Huan thought of was the point in the huge PSTN—the program-controlled digital telephone exchange, especially the Private Private Exchange that serves specific enterprises or institutions.
BranchExchange is PBX.

The main task of the PBX is to complete the telephone exchange between extensions in the system and with the PSTN. The most obvious advantage is to reduce telephone charges by processing the line conversion within the system, and it can also add some service functions that the telephone company does not provide, such as smart search. line, user call, dial extension, etc.

In the PBX structure, the single-chip microcomputer used for data processing and control is Tang Huan's housekeeping skill. As for the R&D engineers of other technologies, there are many companies that can recruit people.

Besides, Huawei started out by making switches. Tang Huan has too much experience to learn from.

On the other hand, the most practical way to connect a PC to the PSTN at the moment is probably a modem.

As early as 1962, AT&T released the first commercial modem Bell103.

By 1978, American Dennis Hayes and his partner Dale Heatherington successfully sketched the prototype of a smart modem at the dining table.That same year, at the age of 29, Hayes founded the Hayes Computer Products Company in Atlanta.

Dennis Hayes loves Chinese culture, not only took the Chinese name He Danyi for himself, but also married a Chinese Ningbo native.

He Danyi's company successfully developed the Hayes Smart Modem in 1981, which is the Hayes Smart Modem. This product is a real standard smart modem, which is a major progress.

Before the advent of smart modems, in order to establish a connection, almost all old-fashioned modems required manually dialing the other party's number on the telephone, and then putting the handset in the AcousticCoupler that came with the modem, a kind of sound coupler with two rubber cups. A device composed of devices used to convert between sound and electrical signals.

With a smart modem, in addition to not requiring a sound coupler, more importantly, the smart modem can be connected directly to a standard telephone line or socket, and then the computer can automatically complete the function of connecting the phone and dialing the number.

It can be said that this change greatly simplifies the installation and use of the electronic bulletin board system or BBS.

It turns out that in that time and space, although He's was finally abandoned by the market, it relied on its own first-mover technology advantages to occupy a dominant position in the modem field for a long time. The AT command set it proposed has almost become the industry standard, and many Smart modems of other brands will expressly state Hayes-Compatable on the packaging, which means they are compatible with the Hayes standard.

At first, Tang Huan didn't pay much attention to this industry that was refined down to the very end. He planned to wait for the development of the Fangyuan second-generation computer to be basically finalized, and then purchase it from He's as needed.

But smart modems were prototyped incidentally for the development of fax servers, and it would be a shame if they weren't put to good use.

And if users can use Fangyuan computers and smart modems, and network operators can use telephone switches developed according to their own design goals, maybe the early dial-up Internet access in the previous life will appear more smoothly.

The only thing worth worrying about is that the research and development and operation of telephone exchanges must be very expensive in the early stage. Under the principle of isolation of non-related industries established by myself, I don’t know whether the incubator Zheru America can rely solely on its own ability to attract money. Take on this task.

"Do you think our newly developed digital fax machine is attractive to wealthy people like the Xiangjiang Police Department?" Tang Huan asked Zhou Weikun beside him.

"Only in terms of function, it is very advantageous, but I don't know what kind of strategy it is in terms of pricing." Zhou Weikun pondered, "But we can follow Feng Xingjun's routine, first pull it on our ship, and then go out step by step Squeeze profits."

"Your cooperation is becoming more and more tacit." Tang Huan shook his head and laughed, "In this case, we have to work hard on product cost control. I just happened to go to RB to see if Sharp can produce a batch of OEM products. , now RB has the highest enthusiasm to approach us in the company.”

Everyone discussed the issue of digital processing fingerprints until after get off work, and the technical solutions were finally finalized one by one.

Tang Huan let out a long breath, returned to his office, raised his neck and drank the tea in the cup in one gulp.

After that, Tang Huan began to write a research and development plan for a program-controlled digital telephone exchange. It wasn't until his stomach growled that he remembered that he hadn't eaten dinner yet.

There were quite a few secretaries and bodyguards, but no one cared whether he was starving or not. Tang Huan picked up the phone complaining, completely forgetting that he himself had made an agreement not to easily disturb his work.

Tang Huan originally wanted someone else to prepare dinner for him, but he remembered Zhao Yazhi who had mixed with him in the past few days, so he called the apartment.

Soon, the phone was connected, and Zhao Yazhi's gentle voice came. Tang Huan lifted his spirits and asked, "Is the apartment ready? I haven't had dinner yet, can I come to your place to solve it?"

"Then come here." Zhao Yazhi agreed with a smile.

……

The high-end apartment that Tang Huan gave to Zhao Yazhi was located near the broadcasting channel where TVB was located, and he quickly rushed over.

"Let's cook noodles, it's quick and convenient." Zhao Yazhi leaned out from the kitchen and said to Tang Huan who was changing shoes at the door.

"Okay." Tang Huan agreed, and walked into the living room to look at the layout, which was very elegant and gave him a feeling of home. When he came, the heat in his heart could not help but cool down slowly, and his heart became warm.

"My personality is indeed very complicated." Tang Huan murmured to himself, sat comfortably on the sofa, and asked casually: "Azhi, I'm going to RB, you can take a trip along the way."

"No, before becoming a flight attendant, I still had the dream of traveling around, but now it's gone." Zhao Yazhi refused politely.

"Hey, it seems that you have to use force for being so shameless." Tang Huan stood up with a threatening expression on his face.

(End of this chapter)