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Anonymous users2024-02-10The communication method that uses "electricity" to transmit messages is called electrical communication.
Electrical communications can generally be divided into two categories: one is called wired communication, and the other is called radio communication. Radio communication is a communication method that uses radio waves to transmit information, and it can transmit sound, text, data, images, etc.
Compared with wired communication, there is no need to erect transmission lines, the communication distance is long, the mobility is good, and the establishment is rapid; However, the transmission quality is unstable and scattered, the signal is easy to be interfered with or intercepted, easily affected by natural factors, and the confidentiality is poor.
Radiocommunication is a communication method that modulates the sound, text, data, images and other electrical signals that need to be transmitted on radio waves to each other through space and the ground, and uses radio electromagnetic waves to transmit information in space.
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Anonymous users2024-02-09Wireless stove radio broadcasting belongs to () communication.
a.Simplex communication.
b.Half-duplex communication.
c.All hands and shuang, quietly communicate.
d.Simplex or half-open slag duplex communication.
Correct Answer: a
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Anonymous users2024-02-08Differences: 1. Wireless communication mainly includes microwave communication and satellite communication: microwave is a kind of radio wave, and the distance it transmits is generally only tens of kilometers.
But microwaves have a wide frequency band and a large communication capacity. Microwave communications require the construction of a microwave relay station every few tens of kilometers. Satellite communication is the use of communication satellites as relay stations on the ground to establish microwave communication links between two or more earth stations or between mobile objects.
2. Zheng Zhixin is a communication mode between mobile users and fixed-point users or between mobile users: one or two parties on both sides of the communication are in motion. Including land, sea and air mobile communications.
The frequency bands used are low, mid, high, VHF and UHF. The mobile communication system consists of a mobile station, a base station, and a mobile exchange office. If it wants to communicate with a mobile station, the mobile exchange office sends a call to the whole network through each base station, and the called station sends an answer signal after receiving the dust, and the mobile exchange allocates a channel to the mobile station after receiving the answer, and transmits a signal from the channel to make it ring.
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Anonymous users2024-02-07Electromagnetic waves that do not use wires are wireless communications.
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Anonymous users2024-02-061. High frequency, strong penetration, low frequency, weak penetration, as above: mobile phone signal is a high-frequency signal, generally only 900 trillion in small cities, 1800 trillion in large cities or populous cities, and only 90 to 100 trillion in broadcast signals.
2. The transmission tower is different, the base station of the mobile phone signal is managed by the operators of China Mobile, China Unicom and Telecom, while the radio is a radio station that belongs to the news category.
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Anonymous users2024-02-05CMMB mainly uses the technology of satellite communication network + terrestrial mobile communication network to realize the mobile transmission of satellite TV signals. It has the following advantages: Profit depends on advertising, and ordinary consumers can watch it for free.
Compared with traditional TV, it is portable, mobile, and interactive. Not only can you "watch" TV, but you can also "listen" to TV and "read" TV.
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Radio plays an important role in our lives, first of all, it should be said that it is radio communication, that our daily most common mobile phone is the most popular radio communication, this network system composed of mobile phones, base stations, switching terminals and other equipment greatly facilitates our lives, followed by private network communication, in fact, CDMA was first developed for the army, this system has the characteristics of good confidentiality, signal stability, etc., most of the communications used by the army now have frequency hopping technology, That is, several parties to the communication can switch frequencies at any time according to certain rules, so that they are less likely to be intercepted. Now when it comes to radio communication, most of them refer to radio communication, such as in disasters, when the base station or switching system can not work, radio communication can play its advantage of not relying on network communication, in emergency communication can be said that radio communication has an irreplaceable role, this means of communication is also widely used in armed police, fire protection, forestry departments, etc., and amateur radio amateurs are also one of the users of this communication. Then there's satellite communication, which we see now is transmitted through satellite signals, and when astronauts talk to ground crews, it's also a kind of radio communication. >>>More
Controlled control is a punishment that is adjudicated by the people's court in accordance with the law, and does not detain minor criminals, but restricts a certain degree of freedom under the control of the public security organs and public supervision. Surveillance is set for a certain period of time, and the offender must not be placed under indefinite control. The period of control is between 3 months and 2 years.
internal machine; There are aluminum thorn sheets (heat exchangers) (not to mention condensers and evaporators when it is used for both cold and warm purposes)! There's a tank fan motor! There's a computer board with a drain fan indicator. >>>More