Transmission medium
The transmission medium is the physical path connecting the sender and the receiver in the network, and the carrier that actually transmits information in the communication.
Commonly used transmission media are: twisted pair, coaxial cable, fiber optic cable and wireless communication and satellite communication channels.
Twisted pair consists of two, four or eight insulated wires arranged in a regular spiral structure.
Shielded twisted pair STP and unshielded twisted pair UTP.
The shielded twisted pair consists of an external protective layer, the shield layer and multiple pairs of twisted pairs.
The unshielded twisted pair is composed of an external protective layer and multiple pairs of twisted pairs.
Three types of lines, four types of lines, five types of lines.
The twisted pair is used as a long-distance intermediate line, the maximum distance can reach 15 kilometers; when used in a 100Mbps local area network, the maximum distance from the hub is 100 meters.
Coaxial cable consists of inner conductor, outer shielding layer, insulating layer and outer protective layer.
Divided into: baseband coaxial cable and broadband coaxial cable.
Single-channel broadband: Broadband coaxial cables can also be used for high-speed digital communications on only one communication channel.
Fiber optic cables are simply referred to as optical cables.
It is composed of optical fiber core, optical layer and external protective layer.
At the fiber launch end, two main light sources are used: light emitting diode LED and injection laser diode ILD.
Optical fiber transmission is divided into single-mode and multi-mode. The difference is that the angle with the brazing axis is either single or multiple light propagation.
Single-mode fiber is superior to multimode fiber.
There are two ways of electromagnetic wave propagation: 1. It is free to spread in space, both wirelessly.
2. In a limited space, the existing way of transmission.
Mobile communication: mobile and fixed, communication between mobile and moving objects.
Mobile communication means:
1 Wireless communication system.
2 Microwave communication system.
Signals with a frequency of 100MHz-10GHz are called microwave signals, and their corresponding signal wavelengths are 3m-3cm.
3 Cellular mobile communication system.
The multiple access methods are mainly: frequency division multiple access FDMA, time division multiple access TDMA and code division multiple access CDMA.
4 Satellite mobile communication system.
Commercial communications satellites are generally launched in synchronous orbits of 35900km above the equator
Any QI enabled device like iPhone X/ 8/8Plus, Galaxy, Samsung S7,S7 Edge, S6,S6 Edge, Nexus 4/5/6 (NOTE: Other device have no wireless charging function except putting on extra receivers.)
Starts the moment you place down any Qi-enabled device or device equipped with a Qi-compatible cover. No cables or USB interface required. Input: AT LEAST 5V/2A; Output: 5V/1A
Wireless Charger,Universal Wireless Charger,Portable Wireless Charger,Mobile Wireless Charger
Shenzhen Waweis Technology Co., Ltd. , https://www.waweis.com