How many nanometers is the s9i miner

1. S9i is 14th / s. according to the current unit difficulty, it can dig out 0.01057560btc per month. At the current cost of electricity and mining machinery, it takes about 130 days to recover the cost. The most important choice is low electricity price

2. Bridge mode, suitable for other router dial-up and computer dial-up users (similar to traditional ADSL, optical cat only as modem)
routing mode, it can directly dial up the Internet, and provide DHCP function (provide IP for multiple computers to let them access the Internet)
the above two can be called_ internet_ The switch function can be realized by configuring the LAN port and LAN port in the link of
LAN port (all routers have this function, if you need to set the domain, please set the VLAN)

to realize all this, please get the super password of lightcat first

all hands~~~

3. Schrodinger's cat theorem is that for the unobservable things, its state is unknowable

"Schrodinger's cat" theorem tries to test the uncertainty of quantum theory with an ideal experiment. That is, in a closed box, there is a live cat and a bottle of poison. When decay occurs, the bottle is broken and the cat is poisoned. According to common sense, a cat may be dead or alive. Quantum mechanics tells us that there is an intermediate state where the cat is neither dead nor alive until we observe what happens.

4. There are a lot of things copied upstairs. Who can see so many. To put it simply, a cat is a modem. The computer receives digital signals, while the ordinary telephone line can only transmit analog signals. Therefore, the cat needs to demolate the analog signals on the telephone line into digital signals for the computer to receive, and molate the digital signals sent by the computer into analog signals transmitted on the telephone line for transmission to the computer room.

5.

Optical fiber communication has rapidly developed into the main form of information transmission because of its advantages of frequency bandwidth and large capacity. To realize optical communication, optical molation and demolation must be carried out. Therefore, as the key device of optical fiber communication system, optical modem is receiving more and more attention

There are two kinds of optical molators: direct molator and external molator, and there are two kinds of optical demolators: with and without built-in preamplifier. Direct molator and demolator with built-in preamplifier are the research focus of this project. Direct molation has the advantages of simplicity, economy and easy implementation, while demolator with built-in preamplifier has the characteristics of high integration and small volume, That is to transform the signal to a frequency suitable for transmission. Generally speaking, molation is to transform baseband signal into a higher frequency band-pass signal

molation is a process of using baseband signal to change the amplitude, phase or frequency of high frequency carrier according to certain rules[ 1]

optical cat

optical cat, also known as single port optical transceiver, is a proct designed for special user environment. It uses a pair of optical fibers for single E1 or single V.35 or single 10baset point-to-point optical transmission terminal equipment. As the relay transmission equipment of local network, this equipment is suitable for optical fiber terminal transmission equipment of base station and leased line equipment

for multi port optical terminals, they are usually called "optical terminals", while for single port optical terminals, they are generally used in the user end, which work like baseband modems commonly used for WAN special line (circuit) networking, and they are called "optical cat" and "optical modem"

there are E1 optical cat, Ethernet optical cat and V35 optical terminal, which are to configure corresponding service interfaces according to customer's requirements. E1 optical cat transmits E1 signal through optical fiber, Ethernet optical cat transmits 2m Ethernet signal through optical fiber, and V35 optical cat transmits V35 signal through optical fiber

optical cat is a kind of equipment similar to baseband modem (digital modem), which is different from baseband modem in that it is connected with optical fiber special line and optical signal. Using photoelectric signal conversion and interface protocol conversion to access router, it belongs to a kind of wide area network access, which is often referred to as optical fiber access. As long as there is optical fiber, optical cat is needed to convert optical signal[ 2]

working principle

Edit

the equipment of optical cat adopts large-scale integrated chip, with simple circuit, low power consumption, high reliability, complete alarm state indication and perfect network management function

optical cat is a device similar to baseband modem (digital modem). Different from baseband modem, it is connected to optical fiber special line, which is optical signal

it is used for the conversion of photoelectric signal and interface protocol in Wan, and it is used to access router and WAN access. Photoelectric transceiver uses the conversion of photoelectric signal in LAN, but only the conversion of signal, without the conversion of interface protocol

application scope

Edit

Ethernet optical cat is mainly used when the distance is more than 20km and the intermediate needs to be transferred through SDH / PDH and other optical transmission equipment. Generally speaking, the speed of optical cat is packaged in 2M circuit, so the difference between optical transceiver of optical cat lies in its speed. Optical cat is 2M and optical transceiver is 100m[ 3]

general application scenarios:

Customer - Ethernet optical cat - optical cable - E1 optical cat - 2m cable - local SDH optical transceiver - another local SDH optical transceiver - PDH optical transceiver - E1 to Ethernet coordination - customer equipment (Ethernet switch or computer, etc.). Of course, there are V.35 light cat, V.24 light cat, RS-232 light cat and so on[ 3]

composition

Edit

the optical modem is composed of sending, receiving, controlling, interface and power supply. The data terminal equipment provides the transmitted data in the form of binary serial signal, which is converted into the internal logic level through the interface and sent to the transmitting part, and then molated into the signal required by the line through the molation circuit and sent to the line

the receiving part receives the signal from the line, and after filtering, anti molation and level conversion, it returns to digital signal and sends it to the digital terminal equipment. Similar to the molation and demolation of high frequency carrier in electrical communication, the optical modem can molate and demolate the optical signal. Whether it is analog system or digital system, the electrical signal with information input to the optical transmitter is converted into optical signal by molation

the optical carrier is transmitted to the receiver through the optical fiber line, and then the receiver converts the optical signal into electrical signal through demolation[ 4]

the optical molator is an E / O conversion component composed of microwave packaged high-frequency DFB laser diode, APC and ATC control circuit. The UHF laser diode is directly molated by RF microwave signal to generate intensity molated optical signal, which is coupled into a single-mode optical fiber. After about 5km optical fiber transmission, the O / E conversion is completed by the optical demolator, The optical demolator is composed of PD mole of high speed transimpedance amplifier and broadband low noise amplifier

the conversion must ensure high linearity and low distortion transmission, so it is completed by recing RF input power and increasing amplifier gain. The key point of the design lies in the microwave packaging and impedance matching of the device. The equivalent circuit of the device is simulated, and the reasonable coplanar microstrip circuit is designed. Finally, the traveling wave and complex conjugate matching are achieved by CAD Optimization. The technical problems of high gain preamplifier and recing third-order intermolation in the system should be solved

[1]

single E1 optical transceiver

Edit

single E1 optical transceiver is a device that molates the E1 signal of G.703 to the optical fiber for transmission

single V.35 optical transceiver: the single V.35 optical transceiver provides a V.35 data interface with n * 64kbit / s framing

Ethernet optical transceiver (2m bandwidth): 2m bandwidth Ethernet optical transceiver provides a 2m bandwidth Ethernet interface It can be used with single E1 optical transceiver and E1 converter

Ethernet optical transceiver (10m bandwidth): the 10m bandwidth Ethernet optical transceiver provides one Ethernet interface and four E1 interfaces

Ethernet interface bandwidth (2-10) m is adjustable, when the bandwidth increases, it needs to occupy E1 interface, every 2m bandwidth increase needs to occupy an E1 interface

when the Ethernet bandwidth is 10m, four E1 interfaces are not available Used with 5e1 optical transceiver and 5e1 converter)

integrated network management rack: the integrated network management rack can be mixed with various cards of optical modems, converters and optical terminals

the unified network management card can satisfy the centralized network management and maintenance of all equipment. The device provides 16 service slots, network management slots and 2 power slots

technical index

optical port

optical wavelength: 1310nm

transmitting optical power: not less than - 10dBm

receiving sensitivity: not more than - 37dbm

connection mode: FC

E1 interface

nominal bit rate: 2048kbit / s

line code: HDB3

impedance: 75 Ω

in line with ITU G.703 recommendations

V.35 interface

V.35 standard rate, support pure 2048kibt / s and N * 64kbit / s, according to the actual needs of users can choose

DTE DCE mode can be selected according to the line, and the data and clock level can meet the ITU-T Recommendation V.35

Ethernet interface

interface rate: support 10 / 100M adaptive access

transmission rate: support pure 2M and transparent transmission pure 10m, according to the actual needs of users can choose

plex mode: support half plex mode Full plex mode

physical interface: the newer version of RJ45 can also support RJ11

fully in line with IEEE802.3 LAN protocol standard [5]

working principle

baseband modem consists of sending, receiving, control, interface, control panel and power supply. The data terminal equipment provides the transmitted data in the form of binary serial signal, which is converted into the internal logic level through the interface and sent to the transmitting part, and then molated into the signal required by the line through the molation circuit and sent to the line. The receiving part receives the signal from the line, and after filtering, anti molation and level conversion, it returns to digital signal and sends it to the digital terminal equipment. Optical modem is a kind of equipment similar to baseband modem, which is different from baseband modem in that it is connected with optical fiber special line and optical signal

indicator light description

Table 1: [6]

indicator light

status

description

WPS

normally on

WPS function enabled

flashing

there are Wi Fi terminals accessing

off

WPS function is not activated

WLAN

always on

the WLAN function is enabled

flashing

data transmission

off

WLAN function is not enabled

USB

normally on

USB port is connected, but no data transmission

flash (2 times / s)

data transmission

off

the system is not powered on or the USB port is not connected

Tel1 ~ tel2

normally on

Tel interface has established a connection with the voice server

flash (2 times / s)

Tel interface has established a connection with the voice server and is off hook or ringing

slow flash (1 time / 2 seconds)

Tel interface is registering with the voice server

off

Tel interface does not establish a connection with the voice server

lan1 ~ lan4

normally on

Ethernet connection is normal

flicker

Ethernet interface has data transmission

off

Ethernet connection not established

Los / PON

as shown in Table 2

power

green light always on

power on

off

power off

Table 2:

status

number

Indicator Status

description

PON

Los

1

flash (2 times / s)

off

PON terminal is establishing connection with upper equipment

2

normally on

off

PON terminal has established connection with upper equipment

3

off

slow flash (1 time / 2 seconds)

PON terminal is not connected with optical fiber or no optical signal

4

flash (2 times / s)

slow flash (1 time / 2 s)

the received optical power is not in the normal range of optical reception

class B + range: - 27 DBM - - 8dbm

class C + range: - 30dBm - - 8dbm

5

off

normally on

PON terminal is disabled by the upper equipment or the PON terminal has abnormal lighting, please contact the service provider

6

off

off

7

flash (2 times / s)

flash (2 times / s)

8

slow flash (1 time / 2 s)

slow flash (1 time / 2 s)

PON hardware failure

6. From the point of view of quantum mechanics, Heisenberg's uncertainty principle is applicable to all physical objects, but its effect is not weak and can be ignored. The essence of the uncertainty principle is to tell us that the various physical quantities of microscopic particles are uncertain, not that we are uncertain. Quantum mechanics shows us a world which is essentially and objectively uncertain. In depth research will involve some deep physical philosophy issues, such as the essence of physical theorem is statistical (such as quantum mechanics) or deterministic (into classical mechanics and relativity). Uncertainty principle is the basis of quantum mechanics, and its important significance lies in the foundation of quantum mechanics. Without quantum mechanics, where can Microelectronics come from, where can computers come from, That's the answer. The so-called Schrodinger's cat is just a censure to the explanation of the fundamental Hagen School of quantum mechanics. It is just a metaphor of a micro process to a macro process. It can't be true. Otherwise you will fall into the abyss of idealism

7. Schrodinger's cat

name

Schrodinger's cat
also known as Schrodinger's cat
English Name: Schr & ouml; dinger' The concept of cat is an ideal experiment of quantum theory
experiment content: the cat is very pitiful. She (assuming this is a female cat to arouse more pity) is sealed in a secret room with food and poison. There is a hammer on the poison bottle. The hammer is controlled by an electronic switch, which is controlled by radioactive atoms. If the nucleus decays, the alpha particles will be released, the electronic switch will be triggered, the hammer will fall, the poison bottle will be smashed, and the cyanide gas inside will be released, and the female cat will surely die. This cruel device was designed by Schrodinger, so the female cat is called Schrodinger cat< In 1935, Schrodinger published a paper entitled "the state of quantum mechanics". In Section 5 of the paper, Schrodinger described the cat experiment, which is often regarded as a nightmare. Copenhagen School said that before the measurement, the state of a particle is ambiguous, When a radioactive atom decays is completely probabilistic. As long as it is not observed, it will be in the superposition state of decay / non decay. Only when it is measured, it will randomly choose a state to appear. So let's put this atom in an opaque box and keep it in this superposition state. Now Schrodinger imagined a delicate device with ingenious structure. Every time an atom decays and emits a neutron, it triggers a series of chain reactions. The final result is to break a gas bottle in the box, and at the same time, there is a poor cat in the box. The thing is obvious: if the atom decays, the gas bottle will be broken and the cat will be poisoned. If the atom doesn't decay, the cat will live well

Natural inference: when they are locked in the box, because we did not observe, the atom is in the superposition state of decay / non decay. Because the state of the atom is uncertain, so the state of the cat is also uncertain. Only when we open the box and look at it, can the final conclusion be reached: either the cat lies dead in the box, or it meows. The question is, what was the cat like before we opened the box? It seems that the only possibility is that it is in the superposition state like our atoms, and the cat was caught in a dead / alive mix

is a cat both dead and alive? It's in a state of dead and dead? It's too much of a conflict with common sense, and it's also bizarre from a biological point of view. If a live cat comes out of the box, if it can speak, will it describe the strange feeling of dead / alive superposition? I'm afraid not. In other words, the concept of Schrodinger's cat is proposed to solve the paradox brought by Einstein's theory of relativity, that is, the theory of parallel universe< Although it has been more than a century since the birth of quantum theory, it has been more than half a century since its prosperity. However, the confusion caused by quantum theory still puzzles people. As Bohr famously said, "anyone who does not feel confused when hearing quantum theory for the first time must not understand it." Schrodinger's cat is a representative of many quantum puzzles. This cat is very pitiful. She (assuming this is a female cat to arouse more pity) is sealed in a secret room with food and poison. There is a hammer on the poison bottle. The hammer is controlled by an electronic switch, which is controlled by radioactive atoms. If the nucleus decays, the alpha particles will be released, the electronic switch will be triggered, the hammer will fall, the poison bottle will be smashed, and the cyanide gas inside will be released, and the female cat will surely die. This cruel device was designed by Schrodinger, so the female cat is called Schrodinger cat

the decay of atomic nucleus is a random event. All physicists can know precisely is the half-life, the time required for half decay. If the half-life of a radioactive element is one day, after one day, the element will be reced by half, and after another day, the remaining half will be reced. But physicists don't know when it decays, in the morning or in the afternoon. Of course, physicists know the probability that it decays in the morning or afternoon - the probability that a female cat will die in the morning or afternoon

if we don't lift the lid of the secret room, according to our experience in daily life, we can conclude that the female cat is either dead or alive. These are her two eigenstates. However, if we use Schrodinger equation to describe Schrodinger cat, we can only say that it is in a superposition state of living and not living. Only when we lift the lid can we know exactly whether the female cat is alive or dead. At this time, the wave function of the cat immediately shrinks from the superposition state to an eigenstate

quantum theory holds that if we don't open the lid and observe, we will never know whether the female cat is alive or dead, and she will always be in a half dead state. This is a serious violation of our daily experience. We should either die or live. How can we be half dead and half alive< According to the explanation of quantum mechanics, the cat in the box is in the "dead live superposition state" - dead and alive! You have to wait until you open the box to see the cat Please note that! It's not discovery, it's decision. It's fatal to look at it As Prince Hamlet said, "it's really a question whether to die or to live." It's only when you open the box that the superposition state suddenly ends (collapse in mathematical terms), that Prince Hamlet's hesitation finally ends. We know the certainty of a cat: dead or alive. The advantage of Copenhagen's interpretation of probability is that there is only one result, which is consistent with what we have observed

but there is a big problem: it requires the wave function to collapse suddenly. But there is no formula in physics to describe this collapse. For a long time, however, physicists have accepted Copenhagen's interpretation out of pragmatism. The price is: violation of the Schrodinger equation. No wonder Schr? Dinger has been worried<

looking for Schrodinger cat

Copenhagen interpretation has become a "orthodox" and "standard" interpretation for a long time. But the immortal cat has always been a nightmare for physicists. What glibin wants to tell us in looking for Schrodinger's cat is where the Copenhagen interpretation failed and what interpretation can replace it

in 1957, Everett's "multi world interpretation" seemed to bring good news to people, although no one took it seriously at first because it was so strange. Glibin believes that multi world interpretation has many advantages, so it can replace Copenhagen interpretation. Let's briefly introce Everett's multi world interpretation

glibin wrote in his book: "Everett... Points out that both cats are real. There is a live cat and a dead cat, but they are in different worlds. The question is not whether the radioactive atom in the box decays, but whether it decays and does not. When we look into the box, the whole world splits into two versions of itself. The two versions are identical in all other respects. The only difference is that in one version, the atom decays and the cat dies; In another version, the atom doesn't decay and the cat is still alive. "

that is to say, "the atom decays and the cat dies; The two worlds will evolve completely independent of each other, just like two parallel worlds. Glibin obviously appreciated the interpretation, so he went on: "it sounds like science fiction, but... It's based on unassailable mathematical equations, based on the plain, self consistent, logical results of quantum mechanics."“ In the multi world of quantum, we choose our own path through participation. In the world we live in, there are no hidden variables. God can't roll dice. Everything is real. " According to glibin, if Einstein were alive, he might agree with and greatly praise the theory that "without hidden variables, God can't roll dice."

the advantage of this interpretation is that the Schrodinger equation always holds and the wave function never collapses, so it simplifies the basic theory. The problem with it is that the assumption is too bizarre, and the price is that these parallel worlds are all equally real. It is no wonder that someone said: "in the history of science, multi world interpretation is undoubtedly the most bold and ambitious theory put forward at present."

Schrodinger equation

in the mid-1920s, Erwin Schrodinger established an equation which is now known as the branch of quantum mechanics. Later it was called Schrodinger equation: ▽ & sup2; ψ( x，y，z)+(8 π& sup2; m/h²)[ E-U(x，y，z)] ψ( x. Y, z) = 0

quantum theory is one of the important scientific developments in the 20th century. However, e to the huge impact of quantum mechanics on traditional concepts, even the "quantum" proponents and other scientists have tried every means to reject it, or to make a variety of harmonic explanations. In fact, Schrodinger was upset by the results of quantum mechanics. He did not like the binary explanation of wave particle ality and the statistical explanation of wave, and tried to establish a theory that only uses wave to explain

Schrodinger tried to use an ideal experiment to test the implied inaccuracies of quantum theory

imagine a live cat and a bottle of poison in a closed box. When decay occurs, the bottle is broken and the cat is poisoned. According to common sense, a cat may be dead or alive. But quantum mechanics tells us that there is an intermediate state where the cat is neither dead nor alive until we observe what happens

quantum mechanics tells us that nothing is real unless we make observations. Einstein and a few non mainstream physicists refused to accept the theoretical results created by Schrodinger and his colleagues. Einstein believed that quantum mechanics is only a reasonable description of the behavior of atoms and subatomic particles, a phenomenological theory, and it is not the ultimate truth in itself. He said a famous saying: "God doesn't roll dice." He didn't admit Schrodinger's theory of cat's extrinsic state, and thought that there must be an internal mechanism that constitutes the real nature of things. He spent years trying to design an experiment to see if this inner authenticity really worked, but he died before he finished it<

Schrodinger cat state

American scientists announced that they have successfully made six beryllium ion systems realize macroscopic quantum superposition state with completely opposite spin direction, namely quantum force

8. Overview of modem. Some people call it "cat" according to the homophony of modem. We know that the information in a computer is a digital signal composed of "0" and "1", but only analog electrical signal is transmitted on the telephone line. Therefore, when two computers want to transmit data through the telephone line, they need a device to be responsible for the conversion of digital to analog. This DAC is the modem we are going to discuss here. When the computer sends data, the modem first converts the digital signal into the corresponding analog signal. This process is called "molation". Before the molated signal is transmitted to another computer by telephone carrier, the receiver's modem is also responsible for restoring the analog signal to the digital signal recognized by the computer. This process is called "demolation". It is through such a digital to analog conversion process of "molation" and "demolation" that the remote communication between two computers is realized< Generally speaking, according to the form and installation mode of modems, they can be roughly divided into the following four categories:

1. External modems

1. External modems are placed outside the chassis and connected to the host through serial communication port. This kind of modem is convenient, flexible and easy to install. The flashing indicator light is easy to monitor the working condition of modem. But the external modem needs to use additional power and cable

2. Built in modem

when installing the built-in modem, the chassis needs to be disassembled, and the interrupt and COM port need to be set, so the installation is cumbersome. This kind of modem needs to occupy the expansion slot on the motherboard, but does not need additional power and cable, and the price is cheaper than the external modem

3. PCMCIA plug-in modem

the plug-in modem is mainly used for notebook computers, and its volume is slim. With mobile phone, mobile office can be easily realized

4. Rack modem

rack modem is equivalent to centralizing a group of modems in a box or shell and supplying power by a unified power supply. Rack modem is mainly used in the central computer room of Internet / Intranet, telecommunication bureau, campus network, financial institutions and other networks

in addition to the above four common modems, there are ISDN modems, cable modems and ADSL modems. Cable modem uses cable of CATV to transmit signal. It not only has the function of molation and demolation, but also integrates router, hub and bridge. The theoretical transmission speed can reach more than 10Mbps. Through cable modem, each user has an independent IP address, which is equivalent to having a personal dedicated line. At present, Shenzhen Cable TV Tianwei network company has launched this Internet access service based on cable TV network, with the access rate of 2mbps-10mbps< Second, modem is only used for data transmission. However, with the continuous growth of user demand and fierce competition among manufacturers, there are more and more "two in one" and "three in one" modems in the market. In addition to data transmission, these modems also have fax and voice transmission functions

1. Fax mode

in addition to saving the cost of a special fax, there are many advantages: you can directly fax the documents in the computer to the other party's computer or fax machine without printing the documents first; The received fax can be saved or edited conveniently; The utility model can overcome the problem that the handwriting of ordinary fax machine graally fades e to the use of thermal paper; Because modem uses error correction technology, fax quality is better than ordinary fax machine, especially for graphic fax. At present, most fax modems follow V.29 and V.17 fax protocols. Among them, V.29 supports 9600bps fax rate, while V.17 supports 14400bps fax rate

2. Voice mode

voice mode mainly provides telephone recording and message and full plex hands-free call function, which truly integrates the telephone and computer. Here, we mainly discuss a new voice transmission mode DSVD (digital simultaneous voice and data). DSVD is a voice transmission standard proposed by Hayes, Rockwell, U.S. robotics, Intel and other companies in 1995. It is an extension of the existing v.42 error correction protocol. DSVD adopts the technology of digital voice and data simultaneous interpreting of Digi Talk, enabling Modem to transmit data on the normal telephone line while making calls.

DSVD modems reserve 8K bandwidth (some modems reserve 8.5k bandwidth) for voice transmission, and the rest of the bandwidth is used for data transmission. Voice will be compressed before transmission, and then integrated with the data to be transmitted, and transmitted to the other user through telephone carrier. At the receiver, Modem first separates speech from data, then decompress the voice signal and convert to digital / analog, so that the simultaneous interpreting of data / voice can be realized. DSVD modem has a wide application prospect in distance teaching, cooperative work, online games and so on. But at present, because the price of DSVD Modem is more expensive than the ordinary Voice Modem, and when it is necessary to realize the function of data / voice simultaneous interpreting, the other party also needs to use DSVD Modem, thus hindering the popularity of DSVD Modem to a certain extent. Thirdly, the transmission rate of modem refers to the amount of data transmitted by modem per second. We usually say 14.4k, 28.8K, 33.6k, 56K, etc., which refers to the transmission rate of modem. The transmission rate is in bps. Therefore, a 33.6k modem can transmit 33600bit data per second. Since the current modems compress the data ring transmission, the data throughput of 33.6k modems can reach 115200bps or even 230400bps theoretically

the transmission rate of modem is actually determined by the molation protocol supported by modem. The V.32, v.32bis, V.34, V.34 +, v.fc and so on that we usually see in the modem packaging box or manual refer to the molation protocol adopted by modem. Among them, V.32 is asynchronous / synchronous 4800 / 9600bps full plex standard protocol; 5. 32bis is an enhanced version of V.32, supporting 14400bps transmission rate; 5. 34 is 28800bps full plex standard protocol; V.34 + is the standard protocol of synchronous full plex 33600bps. The above standards are all formulated by ITU (International Communication Union), while v.fc is 28800bps molation protocol proposed by Rockwell, but it has not been widely supported

when it comes to the transmission rate of modems, we have to mention the popular 56K modems. In fact, the 56K standard has been put forward for many years, but for a long time, there have been two incompatible standards: K56FLEX led by Rockwell and X2 led by u.s.robotics, which make 56K modem not popular. Fortunately, in February this year, with the efforts of the International Telecommunication Union, the 56K standard was finally unified into ITU v9.0. Many modem manufacturers have introced upgrading measures one after another, and modems that really support v9.0 have been blooming everywhere. 56K is expected to become the mainstream of the market in one to two years. By the way, many ISPs in China don't provide 56K access service, so it's better to ask your service provider before purchasing 56K modem to avoid waste

the transmission rates mentioned above are all obtained under ideal conditions. In practice, the speed of modem can not reach the nominal value. The actual transmission rate mainly depends on the following factors:

1. The quality of the telephone line

because the molated signal is transmitted through the telephone line, if the quality of the telephone line is poor, the modem will rece the rate to ensure the accuracy. Therefore, when we connect modem, we should try to rece the length of the connection, cut off the rendant connection, and do not stack it in a circle. In addition, it is better not to use the extension, and the connection should also avoid passing through interference sources such as TV

2. Whether there is enough bandwidth

If a large number of people surf the Internet at the same time, it will cause congestion and congestion, and the transmission rate of modem will naturally decline. Therefore, whether ISP can provide enough bandwidth is very important. In addition, avoiding surfing the Internet ring peak hours is also a solution. Especially when downloading files, the download time will be several times different between peak hours and non peak hours

3. The modem rate of the other party

the molation protocol supported by the modem is downward compatible, and the actual connection rate depends on the lower Party. Therefore, if the other party's modem is 14.4k, even if you use 56K modem, you can only connect at 14400bps< The transmission protocols of modem include molation protocols, error control protocols, data compression protocols and file transfer protocols. We have discussed molation protocols before, and now we will focus on the other three transmission protocols

1. Error control protocol

with the continuous improvement of modem transmission rate, the abnormal mutation of noise and current on the telephone line will cause data transmission errors. Error control protocol is to solve how to ensure the accuracy of data in high-speed transmission. There are two instry standards in current error control protocols: mnp4 and v4.2. Among them, MNP (microcom network protocols) is the transport protocol developed by microcom, including mnp1-mnp10. Due to commercial reasons, micom only publishes mnp1-mnp5, among which mnp4 is one of the widely used error control protocols. V4.2 is an improved version of mnp4 developed by ITU, which includes two control algorithms: mnp4 and lap-m. Therefore, a modem using v4.2 protocol can establish an error free control connection with a modem only supporting mnp4 protocol, and vice versa. Therefore, when we buy modems, we'd better choose those that support v4.2 protocol

in addition, in order to rece the cost, some cheap modem cards in the market do not have hard error correction function, but use software error correction. When you buy, you should pay attention to distinguish, do not be confused by the words "with error correction function" on the packing box< 2. Data compression protocol

in order to improve the amount of data transmission and shorten the transmission time, most modems will compress the data first. Similar to error control protocol, data compression protocol has two instry standards: mnp5 and v4.2bis. Mnp5 adopts two compression algorithms: rnu length coding and Huffman coding, and the maximum compression ratio is 2:1. In v4.2bis, Lempel Ziv compression technology is used, and the maximum compression ratio is 4:1. This is why v4.2bis is faster than mnp5. It should be noted that the data compression protocol is based on the error control protocol. Mnp5 needs the support of mnp4, and v4.2bis also needs the support of v4.2. Moreover, although v4.2 contains mnp4, v4.2bis does not contain mnp5< br />

9. Label: set (8) optical cat (2) network (459) optical cat is "optical modem", which refers to the transceiver that converts optical Ethernet signal into other protocol signals, and also plays the role of molation and demolation. Optical cat is also known as single port optical terminal. As the relay transmission equipment of local network, it is suitable for optical fiber terminal transmission equipment of base station and leased line equipment. For multi port optical terminals, they are usually referred to as "optical terminals". For single port optical terminals, they are generally used at the user end. They work like baseband modems commonly used for WAN special line (circuit) networking, and they are referred to as "optical modem", "optical cat" and "optical modem".

10. Dongxu optoelectronics was listed in 1996 with a cost price of 6.28 at that time. This stock report is all negative. The risk is quite large, so it is suggested to improve the risk awareness. I don't give instructions here. I hope I can help you.