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Network signal and network wiring

2020-11-10 12:02:53 osc_gm4ujyt0

1、 Signal concept and classification

■ Signals are the medium of information transmission , The signal is divided into analog signal and digital signal

● analog signal : The analog signal goes on and on , The signal goes up and down , Not fixed value

● digital signal : Digital signals are discrete , The signal size is a fixed value

2、 Network architecture layering

■ The hierarchy of network architecture is divided into : Access layer , Convergence layer , Core layer
● Access layer : Connect the computer to the local area network , The device used is a layer 2 switch , A hub
● Convergence layer : Cross segment data communication , flow control . The device used is layer 3 switch , Router
● Core layer : High speed forwarding of data . The device used is a router


3、 The spread of radio waves

  • long wave ( Ground waves ) Ultra long range radio and navigation
  • Zhongbo ( Ground wave and sky wave ) Radio and telegraph communications
  • shortwave ( Ground wave and sky wave ) Radio and telegraph communications
  • Ultrashort wave ( Approximate straight line propagation ) radio broadcast , TV , Navigation
  • microwave ( Spread in a straight line )WI-FI, TV , radar

4、 Twisted pair

■ The wire sequence of twisted pair is divided into T568A and T568B
● T568A: White and green , green White orange , blue White and blue , orange White brown , Brown
● T568B: White orange , orange White and green , blue White and blue , green White brown , Brown

5、 Straight and cross lines

■ Straight through cable : The most common cable , If one end of the cable is T568A, And the other end is T568A, If one end is T568B, And the other end is T568B

■ Cross cable : Use two wiring modes at the same time , One end of the cable is T568A, On the other end T568B
● Straight through cables connect dissimilar devices : For example, switch port to router port , Hub port to PC, Switch port to PC
● Cross cables connect similar devices : For example, switch port to switch port , Switch port to hub port , Hub port to hub port , Router port to router port ,PC To the router port ,PC To PC

6、 The classification and difference of optical fiber

■ Single mode fiber : For high speed , The long distance , The high cost , It's hard to terminate , Narrow stamen line , Need a laser source , Dissipation is minimal , Efficient
■ Multimode fiber : For low speed , short distance , The cost is low , It's easier to terminate , Wide stamen line , Good focus , The light source can be laser led , Dissipation is great , Inefficient

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