Communication means

Question 1: What does communication mean? Communication (munication) is the transmission of information. It refers to the transmission and exchange of information from one place to another, and its purpose is to transmit messages. However, with the development of social productivity, people have higher and higher requirements for delivering messages. Among various communication methods, the communication method that uses "electricity" to transmit messages is called telecommunications. This kind of communication has the characteristics of rapid, accurate and reliable, and is almost independent of time, place, space and distance. restrictions, thus it has developed rapidly and been widely used.

Question 2: What are the meanings of communication and communications? What's the difference? What is the difference between communication and communication?

1. Communication and communications

Currently, these two words are used quite frequently, but the scope of their meaning is not clearly unified.

"Communication" in the traditional sense mainly refers to telephone, telegraph, and telex. The "news" of communication refers to message, and media messages are transmitted from one end to the other through the communication network. The content of media messages is mainly voice, text, pictures and video images. The network is mainly composed of electronic equipment systems and radio systems, and the signals transmitted and processed are analog. Therefore, the term "communication" should specifically refer to the process of transmitting the above-mentioned media information using media transmission systems such as telegraphs and telephones.

"Communication" refers only to data communication, that is, the end-to-end transmission of data through computer network systems and data communication systems. The "letter" in communication refers to information, and the carrier of information is binary data. Data is information that can be used to express traditional media forms, such as sounds, images, animations, etc.

Since the old "communication" system has already been transformed into digitalization and computer network, it can be considered that the current data communication system has covered the functions of the past "communication" system. According to this conclusion, the word "communication" should be used more often to express data transmission between the Internet and within a local area network, and the word "communication" should be used as little or as little as possible to avoid conceptual misunderstandings.

2. Nodes and nodes, interconnections and interconnections

In technical articles, you can often see "network nodes" and "network nodes", as well as the terms "interconnection" and "interconnection". Is there a clear definition between them? In fact, this is a purely language issue and has nothing to do with technology. Even if there is confusion, there will be no ambiguity, so these words can be used without any distinction.

3. Protocols and Standards

There are different protocols or standards on the Internet. The concepts of "protocol" and "standard" are similar but different. The protocol is layered. At the low level, it refers to the agreement that all parties in the communication must abide by; at the high level, it refers to the agreement on network application and management. Therefore, the essence of a protocol is an agreement, and it is a formal agreement. For example, IP is the third layer protocol of OSI/RM.

The scope of standards is broader. It includes not only written agreements, but also all uniformly executed rules on the Internet. So standards are sometimes called norms or rules. For example, IEEE 802.3u is a Fast Ethernet standard developed by the Institute of Electrical and Electronics Engineers. It can also be considered as a large protocol set for 100M Ethernet; Category (CAT3, CAT5) is an unshielded dual protocol set by EIA/TIA. The wire standard established by twisted wire can only be called a standard, not a protocol.

2. The same word has different meanings

1. Bandwidth

In network technology, "bandwidth" has different meanings in different applications. One refers to the frequency bandwidth of the network - the frequency band width, which is the difference between the maximum frequency and the minimum frequency of the network signal, the unit is Hertz; the other refers to the maximum transmission rate of the LAN, which represents the data transmission capability of the LAN, the unit is bps.

2. Rate

"Communication rate" is usually divided into two types: one is the number of bits transmitted per unit time, also called bit rate, data transfer rate, data rate or simply rate; the other is the number of bits transmitted per unit time; The number of symbols transmitted within the system is also called symbol rate, modulation rate, baud rate or simply Baud Rate. The bit rate value can be the same as the baud rate value, or it can be different. For example, for a Modem, the bit rate value during operation is much greater than the baud rate value.

3. Media

"Media" (Media) is a word that often appears. It can be understood as an intermediary used to connect two or more things. It is also called media, medium, medium in different applications. , interface, etc., but the meanings are different.

When used in the field of public information dissemination, "media" is called media, such as radio, television, newspapers, magazines, websites, etc., all belong to the media.

When used in computer information processing technology, "media" is called media information. Usually refers to various media such as voice, text, graphics, images, animation, etc., that is, multimedia.

When used in network and communication technology, it is called media media, communication media, and transmission media. The cables, optical cables, radios, microwaves, etc. that we are familiar with belong to this category.

In addition, in the field of software applications, the part of the media information output to the user through the display is called the user interface of the software (...gt; gt;

Question Three: What does communication technology mean? Nowadays, the term communication technology is generally used to refer to science and technology in communication (Internet, telephone, etc.)

Question 4: What does CESP mean in communication? Ethernet. Multi-service platform (CESP-CarrierEthernetMulti-Service Platform)

Question 5: What does the communication assistant service mean? It is a reminder service when the phone is turned off or has no answer or is not in the service area. When the phone is restored to Send text messages to users during normal service to tell you who called you at what time

Question 6: What does IS communication mean? Communication is the use of narrative, description, lyricism, discussion, etc. A technique,

A news report that concretely, vividly and vividly reflects a news event or a typical person

Question 7: What does "mobile communications" mean? It is preceded by the name of the unit and followed by the business Scope

Question 8: What does a correspondence address mean? A correspondence address refers to a valid actual address that can be marked and received on envelopes, mailing items, e-mail boxes, and other mails sent by postal means or the Internet. It usually consists of area name, street name and house number; generally large websites can register a free personal email address, and the email address you apply for is your electronic address.

Question 9: What does RS-485 communication mean. ? Typical serial communication standards are RS232 and RS485, which define voltage, impedance, etc., but do not define the software protocol. Different from RS232, the characteristics of RS485 include:

1. Electrical characteristics of RS-485 Characteristics: Logic "1" is represented by the voltage difference between the two lines being (2-6) V; logic "0" is represented by the voltage difference between the two lines being - (2-6) V. Interface signal level ratio RS-. 232-C is lowered, which makes it less likely to damage the chip of the interface circuit, and the level is compatible with the TTL level, making it easy to connect with TTL circuits.

2. The maximum data transmission rate of RS-485 is 10Mbps. .

3. The RS-485 interface uses a combination of balanced driver and differential receiver, which has enhanced anti-interference ability, that is, good anti-noise interference.

4. The standard maximum transmission distance of the RS-485 interface is 4000 feet, which can actually be up to 3000 meters. In addition, the RS-232-C interface only allows one transceiver to be connected to the bus, that is, a single station capability. The RS-485 interface allows up to 128 transceivers to be connected to the bus. That is, it has multi-station capability, so users can easily establish a device network using a single RS-485 interface.

Because the RS-485 interface has good anti-noise interference, long transmission distance and multi-station capability, it has become the preferred serial interface. Because the half-duplex network composed of the RS485 interface generally only requires two connections, the RS485 interface uses shielded twisted pair transmission. The RS485 interface connector uses a DB-9 9-pin plug socket, the RS485 interface with the smart terminal uses DB-9 (hole), and the keyboard interface RS485 connected to the keyboard uses DB-9 (pin).

RS485 programming

The serial port protocol only defines the transmission voltage, impedance, etc., and the programming method is the same as ordinary serial port programming

Because the RS-485 interface has good The above-mentioned advantages such as excellent noise immunity, long transmission distance and multi-station capability make it the serial interface of choice. Because the half-duplex network composed of the RS485 interface generally only requires two connections, the RS485 interface uses shielded twisted pair transmission. The RS485 interface connector uses a DB-9 9-pin plug socket, the RS485 interface with the smart terminal uses DB-9 (hole), and the keyboard interface RS485 connected to the keyboard uses DB-9 (pin).