"Modern Shunfeng Ear─Telephone" Information Transmission PPT

"Modern Shunfeng Ear─Telephone" Information Transmission PPT

Part One Content: Basic Knowledge Key Points

Knowledge point 1: Electric current transmits information to distant places

1. The microphone of the old-fashioned telephone turns the sound into a changing electric current, and the electric current transmits the information to distant places along the wire. At the other end, the current causes the diaphragm of the earpiece to vibrate, and the information-carrying current becomes sound again.

2. The scientist who invented the telephone in 1876 was (B)

A. Edison B. Bell

C. Oersted D. Faraday

Knowledge point 2 Telephone exchange

3. When a person in Beijing calls a friend in Shanghai, the signal transmission process is from the phone in Beijing to the switch in Beijing through the phone line, and then from the switch in Beijing to the switch in Shanghai through the phone line, and then Upload from the switchboard in Shanghai to the phone of a friend in Shanghai.

4. The early telephone exchanges relied on the manual operation of operators to connect and disconnect; later, automatic telephone exchanges appeared, which were connected through electromagnetic relays; and modern program-controlled telephone exchanges make use of electronic computer technology, and It has more functions and is more convenient to use.

5. The main function of a telephone exchange is (A)

A. Improve line utilization B. Improve communication quality

C. Speed ​​up communication D. Reduce heat loss of lines

Knowledge point 3 Analog communication and digital communication

6. An electrical signal that imitates an acoustic signal is called an analog signal; a signal represented by a combination of numbers is called a digital signal.

7. Digital signal is (D)

A. A signal composed of 10 numbers 0, 1, 2...9

B. Signals represented by different combinations of "·" and "-"

C. A signal composed of 10 numbers 0, 1, 2...9 and letters A, B, C...Z

D. Signals represented by different combinations of different symbols

8. Which of the following descriptions of analog signals and digital signals is correct (D)

A. Digital signals may cause sound and image distortion when transmitted over long distances or amplified multiple times.

B. Analog signals only contain two different states and are simple in form

C. Analog signals can be encrypted with different encodings

D. Digital signals can be easily processed by electronic computers, thus giving full play to the huge functions of computers.

Modern Shunfeng Er Telephone PPT, Part 2: Improvement of Comprehensive Ability

9. There is an electromagnet in the listening (optional "listening" or "talking") tube of the telephone, which uses the magnetic effect of current.

10. The main energy transformation that occurs in the telephone receiver is the conversion of electrical energy into kinetic (or mechanical) energy.

11. A post office operator received a telegram code at work. One of the characters in the code is "00010,00110,00011,00101". Please translate this character according to the following telegram code. The character is Hang.

12. Regarding the microphone and receiver in the telephone, which of the following statements is correct (C)

A. The earpiece converts acoustic signals into electrical signals

B. The microphone converts electrical signals into acoustic signals

C. The earpiece works using electromagnets

D. The microphone works using electromagnets

13. Which of the following statements is correct (A)

A. The microphones of old telephones contain carbon particles and diaphragms.

B. Today’s telephones use analog signals to transmit information

C. In the microphone of an old telephone, the changing current causes the diaphragm to vibrate in the magnetic field and produce sound.

D. The principle of dynamic microphone is the same as that of electric motor.

14. Xiao Lin called his cousin in Shenzhen from Guangzhou. A busy signal came from the receiver and the phone was "busy". This is (D)

A. The phone number at my cousin’s house was not put away.

B. My cousin is talking to someone on the phone

C. There are too many users on the call between Guangzhou and Shenzhen

D. The above situations are all possible

15. Several students are talking about the phone. They have the following statements. Which one do you think is incorrect (B)

A. The wires between the phones carry current signals.

B. Program-controlled telephones do not need to be connected with wires

C. Telephone calls are made through telephone switches.

D. Both the earpiece and the microphone can convert between sound and electricity.

16. Regarding digital communication, which of the following statements is incorrect (C)

A.Digital communication can use two numbers "0 and 1" to form a digital signal to transmit information.

B.Digital communication has strong anti-interference ability and no distortion

C. The signals transmitted by digital communication are exactly the same as the frequency and amplitude changes of sound.

D.Digital communication is much more advanced than analog communication

17. Which of the following signals is not a digital signal (B)

A. In ancient times, soldiers often lit fireworks on beacon towers to convey news of the enemy's invasion to their companions in the distance.

B. The telephone microphone converts the speaking voice into an electrical signal and transmits it to the telephone switch

C. Chinese character telegraph code

D. Sailors raise red flags or blue flags to express information to the other party's ship

Modern Shunfeng Er Telephone PPT, the third part: Expansion, exploration and breakthrough

21. In order to explore the principle of the telephone’s carbon microphone converting sound into signal current, Xiaowen designed the following experiment:

① Connect the power supply, small light bulb, and two carbon rods to form the circuit as shown in the picture. Place one carbon rod horizontally on the other to form a cross. At this time, the light bulb will glow, indicating that the circuit is connected;

②Press the upper carbon rod down with your hand and observe the changes in the brightness of the bulb. The tighter you press the charcoal rod, the brighter the bulb becomes.

(1)What does the above experiment show?

(2) What are the similarities and differences between this experiment and the actual working principle of carbon particle microphones?

(1) The tighter the two carbon rods are pressed, the brighter the bulb becomes, indicating that the contact resistance becomes smaller and the current becomes larger. Therefore, this experiment shows that changing the tightness of the carbon rod contact can change the size of the current in the circuit.

(2) Difference: This experiment converts changing pressure into changing current, while the carbon particle microphone converts changing sound into changing current. Similarity: Both use changes in the tightness of contact between carbon rods or carbon particles to cause changes in resistance, thereby converting changes in the outside world into changes in current.

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