Chapter 180 Telephone Flyer

Lin Hong listened to the dialogue from the mobile phone speaker and became interested in the principle of this thing.

"Interesting function, it can actually receive other people's mobile phone calls, which is equivalent to a small radio station. Is this the SAS system? As far as I know, the SAS system is not that simple, is it? This function reminds him of the radio station he has been playing. But he saw in the bank that the SAS system used by the robber BOSS was not like this.

"This is not a SAS system." Kevin Mitnick hung up the phone.

"This is just a hidden function in the mobile phone. It is a function that mobile phone manufacturers have when producing, but it was accidentally found when studying this mobile phone.

I just want to tell you that our usual phone calls are not safe, and these signals are easy to be intercepted and monitored.

The SAS system is based on such a principle, and the system has a deeper cooperation with the equipment of the telephone and telegraph company, and the functions are naturally much more powerful than this. The FBI has access to the system at any time. Their agents can accurately monitor the specified number and locate the caller. Location, take the initiative to cut off the other party's call... and so on.

When Lin Hong thought that when he was usually on the phone, there might be another person hiding in a corner and eavesdropping quietly, he had a chilling feeling.

In this way, won't any secrets of us ordinary people be known to each other?

I don't know if there is such a situation in China?

"This is indeed a very horrible thing." Lin Hongshen thought that if such a system is abused, it will definitely cause great harm. That's one of the reasons why the FBI wants to hunt down Kevin, right? However, it seems that the whole system has been spread out. The robber boss knows the existence of the SAS system. Did Kevin reveal it?

Although he wanted to ask, Lin Hong finally gave up. He looked at the mobile phone in Kevin's hand and couldn't help saying strangely, "Since someone will monitor the mobile phone, do you still use this? Aren't you afraid of being monitored?"

"Generally speaking, I rarely talk about things that need to be kept confidential on the phone." Kevin said, and then took out a small box from his backpack. "If things are really urgent, you can use this."

"What is this?"

Lin Hong saw that he was holding a small gray box the size of a Walkman in his hand, with several buttons and a loudspeaker.

"This is a dial-up tool. With this, you can control the phone system." Kevin patiently explained, "Now, there are many tools like this, but my one has been modified and can be used in combination with the SAS system, which is more powerful."

Hearing what was raised in his heart, Lin Hong hesitated for a long time and finally asked, "Paul, can you teach me flying skills? I want to know more about the principle.

Kevin smiled and said, "Of course. As I said before, we are the same kind of people. Even if you don't teach us, you will find out sooner or later.

"If you are really interested in this, we can try a phone booth."

Obviously, Lin Hong was completely immune to technical things, so he decided to go to a nearby phone booth with Paul on the spot.

Of course, they told others to go to mǎi to order drinks and mineral water.

"STONE, how much do you know about the telephone system?" On the way to the phone booth, Kevin asked.

"I haven't been exposed to this knowledge, but I have some knowledge about radio. I'm a fire."

"Do you have any knowledge of radio? That can be used quickly. I used to be an ashes-level fire. If I hadn't had the knowledge accumulated from playing radio when I was a child, I wouldn't have explored the telephone system and the computer world more deeply.

Both of them are very enthusiastic about technology and have a superior IQ, and have a lot of common language.

Kevin is actually very happy. In the past two years, he has lived a very lonely life. He can only show himself as Paul. He plays the role of a taciturn person who is not very interested in other things. He is eager to communicate, but even on the Internet, he has no friends at all. It's not that he doesn't want to, but he doesn't dare. He is now a wanted criminal of the FBI. If he accidentally goes out, he may be caught and thrown into prison.

He knew that Lin Hong and he were the same kind of people, and there was no threat to him. Instead of making him suspicious and causing misunderstanding, it was better to tell him directly and frankly. After all, he is doing well here. He doesn't want to change his identity and continue to drift around and hide like before.

On the way to the phone booth, Kevin began to introduce the telephone system to Lin Hong.

The earliest civil telephone system originated from the fully automatic execution switch device of ATT, which originally used pulse signals for dialing.

"I don't know if you've seen an audio dialer. The most common form is a dial dial, which is called a finger wheel."

"Finger wheel? I think I've seen this kind of dialer, but it's in the movie. Lin Hong remembered that in some anti-war movies he had seen before, there was such an old-fashioned phone. When those people wanted to call others, they usually dialed the dial a few times on the turntable with their fingers, and then they could dial the other party's phone.

"The old-fashioned finger wheel can generate a specific pulse signal. This kind of dialing is a time domain processor, which uses the number of pulses to represent the number. For example, one pulse represents 1, two pulses represent 2, and so on, and ten pulses represent 0..."

This kind of pulse has strict parameter characteristics, such as strict requirements for the width, size, spacing and shape of the pulse. If these parameters are changed due to line interference or other reasons, it may cause the telephone program-controlled switch to decode these signals.

Lin Hong didn't know until now that the original principle of the telephone turntable was like this.

Soon, the two of them came to a phone booth in AD.

Kevin pointed to the phone button in the phone booth and said, "The current telephone system has been upgraded, and the telephone dialing no longer uses the previous backward and slow pulse dialing method, but has been changed to this dual-tone multi-frequency dialing method, which is an audio dialing method. The reason why it is called two-tone multi-frequency is that there are a total of eight frequencies, divided into two groups, and then let them be combined, so that there are a total of 16 combinations, which can represent different signals in 16. It represents 10 numbers from 0 to 9 respectively, as well as these special characters and letters on the keyboard.

Lin Hong saw that in addition to ten numbers, there are two special characters "*" and "#" and four letters "ABCD" respectively.

Lin Hong thought for a moment and said, "The upgraded telephone system should also support the previous dialing method."

This is a natural truth, just like a computer. No matter how it is upgraded, it will basically be "forward compatible", which is to consider the previously released software and hardware. Of course, there are very few individual exceptions, but "forward compatibility" is a very important principle. In Lin Hong's mind, telephone upgrade is definitely not something that can be completed in a day or two. In all parts of the United States, there must be some users who still use old-fashioned phones to dial. If this dial-up method is directly abolished, what will they do?

"Yes, pulsed dialing is also possible now. Do you have a local phone number?

"Yes." Lin Hong reported Mu Sitong's mobile phone number to Kevin.

"I'll show you the pulse dial first." He took off the receiver from the phone booth and threw a 25-cent coin into the phone.

Then, Kevin began to pat the fork spring on the public phone quickly and rhythmically.

"Papa"

"Bang"

"Papa"

......

Mei's mobile phone numbers are all ten digits, the first three are the area code, and the area code of New York City is "212". Lin Hong noticed that the order in which Kevin patted the phone fork spring was carried out in this order.

After a while, Kevin said, "Okay, it's connected. Do you want to talk to your aunt?

Lin Hong came up to listen for a while. Sure enough, Aunt Mu Sitong was asking over there, so Lin Hong told her about what he was on the big brother's side. He said a few words briefly and hung up the phone.

It turns out that you can directly pat the fork spring to dial like this. Lin Hong has seen it. If the button of the phone is broken in the future, it can be dealt with in this way.

"This ancient way of dialing is very interesting!" Lin Hong commented.

"This pulse dialing method is relatively backward, and the speed is a little slow. Each pulse signal needs to occupy 100 milliseconds, and the interval in the middle of the signal cannot be less than 40 milliseconds. This must be noted, otherwise there will be an error in dialing." Kevin told Lin Hong other precautions, and then then taught him how to make free long-distance calls.

"Give me a long-distance phone number"

Lin Hong thought for a moment and reported Sun Wu's family number to him. It's the weekend now, and Sun Wu should be at home.

Kevin took off the phone again, then threw a 25-cent coin into the phone again, and then he took out a small gray box from his pocket, put it on the microphone, and pressed one of the buttons.

After a short sound, he put the small box back in his pocket.

"Now we can make a free phone call." Kevin said.

How can you make a free call so easily?

Lin Hong feels very novel. Of course, he is interested in the technology involved, not because he can save money and make phone calls.

Lin Hong answered the phone suspiciously and dialed Sun Wu's number. He chatted with Sun Wu for a while, briefly talked about what happened here, and then talked about the current situation of the eldest brother. He was worried that the master could not contact the eldest brother. Of course, he did not say the specific plan of the eldest brother.

After the call was over, Lin Hong hung up the phone. Kevin pressed the coin button on the phone, and the phone obediently vomited the 25 cents again. That is to say, Lin Hongzhen just made a long-distance call for free. ( To be continued