readx;

Chapter 180: The Telephone Flyer

Lin Hong listened to the conversation coming out of the speaker of his mobile phone and became interested in the principle of this thing. Pen "Fun" Pavilion www.biquge.info

"The interesting feature is that it can receive calls from other people's mobile phones, which is equivalent to a small radio station. This is the SAS system? As far as I know, the SAS system isn't that simple, is it? This feature reminded him of the radio station he had been playing. But he saw in the bank that the SAS system used by the robber boss was not like this.

"It's not a SAS system." Kevin Mitnick hung up the phone.

"This is just a hidden function in the mobile phone, a function that the mobile phone manufacturer has when it is produced, and it was only accidentally discovered when studying this mobile phone.

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

The SAS system is built on this principle, and this system has a deeper level of cooperation with the equipment of the telephone and telegraph company, and the function is naturally much more powerful than this, the FBI has the right to access the system at any time, and their agents can accurately monitor the designated number, can locate the location of the caller, and actively cut off the other party's call...... And so on and so forth. ”

Lin Hong shuddered at the thought that when he was usually on the phone, there might be another person hiding in a corner, eavesdropping quietly.

In this way, wouldn't any secrets of us ordinary people be known to the other party?

I wonder if such a situation exists in China?

"It's a very scary thing indeed." Lin Hong deeply believes that such a system, if abused by others, will definitely cause great harm. That's one of the reasons why the FBI wants to hunt Kevin so badly? But it seems that the whole system has been spread, and the robber boss knows about the existence of the SAS system, is it revealed by Kevin?

Although he wanted to ask, Lin Hong finally gave up. He looked at the mobile phone in Kevin's hand and couldn't help but wonder, "Since someone will listen to the mobile phone, then you still use this?" Aren't you afraid of being spied on? ”

"In general, things that need to be kept secret, I rarely talk openly on the phone." Kevin said, then pulled a small box out of his backpack, "If it's really urgent, you can use this." ”

"What is this?"

Lin Hong saw that he was holding a small gray box similar to the size of a walkman in his hand, with several buttons on it and a speaker.

"It's a dialing tool, and with this, you can have control over your phone system." Kevin patiently explained, "Now, there are many tools like this, but this one of mine has been modified to be used in combination with the SAS system, and it is more powerful. ”

Lin Hong listened to the itch in his heart, hesitated for a while, and finally asked, "Paul, can you teach me the Flyer technique?" I wanted to get to know more about how it works. ”

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

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

Obviously, Lin Hong has no immunity to technical things at all, and decided to go to a nearby phone booth with Paul on the spot.

Of course, they said to others to go buy some drinks and mineral water.

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

"I haven't been exposed to this knowledge, but I have some knowledge of radio, and I'm a ham."

"Got knowledge of radio? That can be picked up quickly. I used to be a hardcore ham, and I wouldn't have been able to explore the telephone system and the world of computers more deeply without the knowledge I had gained as a child playing radio. ”

Both are very passionate about technology and have excellent IQs, and they have a lot of common language.

Kevin is actually very happy in his heart, in the past two years, he has lived a very lonely life, and usually can only show himself as Paul, playing the role of a person who is silent and not very interested in other things. He is eager to communicate, but even on the Internet, he has no friends at all, not because he doesn't want to, but he doesn't dare. He is now a wanted criminal in the FBI, and if he is not careful, he could be caught and thrown into prison.

He knew that Lin Hong was the same kind of person as him, and there was no threat to him, so instead of making him suspicious and causing misunderstanding, it was better to tell him directly and honestly. After all, he is doing well here, and he doesn't want to change his identity and continue to live a life of wandering and hiding like before.

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

The earliest telephone systems used in civilian use originated from AT&T's fully automatic switchgear, which initially used pulse signals for dialing.

"I don't know if you've ever seen an audio dialer, but the most common form is a dial dial, known as a finger wheel."

"Finger wheels? I think I've seen this dialer, but in the movies. Lin Hong remembered that in some of the Anti-Japanese War films he had watched before, there had been this kind of old-fashioned telephone, and those people wanted to call others, usually using their fingers to dial the dial a few times, and they could dial the other party's phone.

"In the old old way, finger wheels could generate specific pulse signals, and this kind of dialing was a time-domain processing method that used the number of pulses to represent the number of numbers. For example, one pulse means 1, two pulses represent 2, and so on, ten pulses represent 0......"

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

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

Soon, the two of them arrived at a phone booth inside 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 backward and slow pulse dialing method of the past, but has 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 because there are a total of eight frequencies, divided into two groups, and then let them be combined in pairs, so that there are a total of 16 combinations that can represent 16 different signals. They represent ten numbers from 0 to 9, as well as these special characters and letters on the keyboard. ”

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

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

It's a natural thing that, just like a computer, no matter how much you upgrade, it's basically "forward compatible" to take into account the software and hardware that has already been released. Of course, there are a few exceptions, but "forward compatibility" is a very important principle. In Lin Hong's mind, phone upgrades are certainly not something that can be completed in a day or two, and there must still be some users who still use old-fashioned phones to dial in various parts of the United States.

"Yes, it is now possible to dial by pulse. Do you have a local phone number? ”

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

"I'll start by showing you how to dial the pulse." He removed the receiver from the phone booth and threw a 25-cent coin into the phone.

Then, Kevin began to tap the fork spring on the public phone in a fast and rhythmic way.

"Bang Bang"

"Smack"

"Bang Bang"

……

Mobile phone numbers in the United States are all ten digits, the first three are the area code, and the area code for New York City is "212".

After a while, Kevin said, "Okay, it's connected." Would you like to talk to your aunt? ”

Lin Hong leaned in and listened, and sure enough, Aunt Mu Sitong was asking over there, so Lin Hong told her about what he was doing with the senior brother, and hung up the phone after a few brief words.

It turned out that it was possible to directly tap the fork spring to dial in this way, Lin Hong saw it, if the button of the phone was broken in the future, he could deal with it in this way.

"It's an old way of dialing!" Lin Hong commented.

"This pulse dialing method is relatively backward, the speed is a bit slow, each pulse signal needs to occupy 100 milliseconds, and the interval between the signals can not be less than 40 milliseconds, this must be noted, otherwise there will be a dialing error." Kevin told Lin Hong about other precautions, and then went on to teach him how to make free long-distance calls.

"Give me an international phone number"

Lin Hong thought about it and reported the number of Sun Wu's house to him, it was the weekend, and Sun Wu should be at home.

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

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

"Now we can call for free." Kevin said.

How easy it is to make a free call?

Lin Hong felt very novel, of course, he was interested in the technology involved, not because he could save money and make phone calls.

Lin Hong took the phone suspiciously, dialed Sun Wu's number, he chatted with Sun Wu for a while, briefly talked about the matter here, and then talked about the current situation of the senior brother, afraid that the master would not be able to contact the senior brother and was worried, of course, he did not say the specific plan of the senior brother.

After the call ended, Lin Hong hung up the phone. Kevin pressed the button on the phone, only to spit out the 25 cents on the phone. In other words, just now Lin Hong really made an international call for free.

*