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Technical information :

DSTCX008 Short Haul Modem MA-12

A modem is a piece of computer hardware that translates a computer's digital signals into pulse signals that can be transmitted along an ordinary telephone line, and these pulse signals can be picked up by another modem at the other end of the line and translated into a language that the computer can understand. This simple process completes the communication between the two computers.

Modem, in fact, is the abbreviation of Modulator (modulator) and Demodulator (demodulator), Chinese called modem (Hong Kong and Taiwan called data machine). According to the homophony of Modem, affectionately called "cat".

The so-called modulation is to convert the digital signal into the analog signal transmitted on the telephone line; Demodulation, the conversion of an analog signal into a digital signal. Collectively called modem.

The English word for MODEM is MODEM, which acts as an "interpreter" for analog and digital signals. There are two kinds of electronic signals, one is "analog signal" and the other is "digital signal". The telephone lines we use transmit analog signals, and the PCS transmit digital signals between them. So when you want to connect your computer to the Internet over a phone line, you have to use a modem to "translate" two different signals. After connecting to the Internet, when the PC sends information to the Internet, because the telephone line transmits an analog signal, it must use a modem to "translate" the digital signal into an analog signal before it can be transmitted to the Internet, this process is called "modulation". When a PC obtains information from the Internet, the information transmitted from the Internet through the telephone line is an analog signal, so the PC

In order to understand them, you must also use the modem to "translate ", a process called" demodulation ". In general, it is called"

Modulation and demodulation.

The English name of MODEM is MODEM, also known as "cat", which is an abbreviation of the two words MODULATER and DEMODULATER. We know that the language between computers is a digital signal consisting of 0s and 1s, while the signal transmitted by telephone lines is an analog signal. Each set of transmissions requires a pair of modems to complete. The A-modem on the A-machine converts the digital signal of the A-machine into an analog signal that can be transmitted by the telephone line, and transmits it to the B-modem through the telephone line. Then the B-modem converts the received analog signal into a digital signal that can be recognized by the computer and transmits it to the B-machine. In this way, the communication between the two computers is realized.

A-machine and A-modem are your computer and demodulator, and B-machine and B-modem are dial-up servers at one end of the telecommunications office. After the connection, the computer and the telecommunications office end of the dial-up server to establish a physical connection, on the basis of the physical connection, you can enjoy the Internet service.

Modems used on ordinary telephone lines are called analog modems. A 56K analog modem has a theoretical maximum download rate of 53,333Bps on a regular line, while a maximum upload rate of 33.6KBps.

On a normal phone line, connect with two 56K modems, with a maximum connection rate of 33.6K. This is because the A-modem download is an upload to the B-modem, and the B-modem download is an upload to the A-modem. Limited by a modem upload rate of up to 33.6KBps on a regular line, the maximum connection rate is 33.6K. Most of the 33.6K modems have been discontinued.

On ordinary telephone lines, with 163, 167 and other ISPs that provide 56K access, you can usually achieve a connection speed of about 50K. This is because the Modem at 163, 167 and other offices is a digital Modem, and if it is combined with a suitable Modem, it can reach or exceed the theoretical value on the ordinary line with good quality.

PLC and DCS system in common

①DCS: Distributed control systems (distributedcontrol systems).

PLC: Programmable Logic Controller (PLC). Both have different emphasis and are advanced.

②DCS focuses more on the process control field (such as chemical, smelting, pharmaceutical, etc.) is mainly the monitoring and adjustment control of some field parameters, while PLC focuses on logic control (machining class). Of course, the current PLC can also deal with process control problems well, but there is no DCS professional.

(3) If the simulation quantity is greater than 100 points, DCS is generally used; If the analog quantity is within 100 points, PLC is generally used.

DCS is a "distributed control system", and PLC is just a control "device", the two are the difference between "system" and "device". The system can realize the functions and coordination of any device, and the PLC device only realizes the functions of this unit.

The DCS network is the central nervous system of the whole system, DCS system usually uses the international standard protocol TCP/IP. It is a safe and reliable double redundancy high-speed communication network, the system is more extensible and open. Because the PLC basically works for a single small system, when communicating with other PLC or host computer, the network form used is basically a single network structure, and the network protocol is often inconsistent with international standards.

All I/O modules of DCS system are equipped with CPU, which can realize the acquisition and output signal quality judgment and scalar transformation, fault charging, random replacement. The PLC module is just a simple electrical converter, there is no intelligent chip, and the corresponding unit is all paralyzed after the failure.

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