"Modern Shunfeng Ear─Telephone" Information Transmission PPT Courseware 5

Description

"Modern Shunfeng Ear─Telephone" Information Transmission PPT Courseware 5

The production and spread of sound:

Sound is produced by the vibration of objects, and all sound-producing bodies vibrate.

Sound propagates through media, and vacuum cannot propagate sound.

(1) Microphone

1. Microphone structure: There is a metal box in the microphone, which is filled with carbon particles and covered with a diaphragm.

2. Microphone characteristics: The contact between the carbon particles is not close, and the overall resistance changes with the tightness of the diaphragm.

Microphone structure:

There is a metal box inside the microphone, which is filled with carbon particles and covered with a diaphragm.

effect

When speaking into the microphone, the diaphragm presses the carbon particles tightly and loosely, and their resistance changes accordingly, and the current flowing through the carbon particles changes accordingly, thus forming a current signal that changes with the sound.

Acoustic signal Electrical signal

(2) Handset

1. Handset structure: There is a permanent magnet in the handset, with solenoids on its two magnetic poles, and a thin iron sheet in front of the magnetic poles.

2. Features of the earpiece: Due to the attraction of the permanent magnet, the thin iron sheet is somewhat bent toward the magnet.

Handset structure:

There is a permanent magnet in the earpiece, with solenoids on its two magnetic poles, and a thin iron sheet in front of the magnetic poles.

effect

Inside the earpiece is a magnet with a coil wound around it and a thin iron diaphragm in front of it. Due to the attraction of the magnet, some of the thin iron diaphragm is bent toward the magnetic pole. When the phone is connected, the receiver and the other party's microphone are equivalent to being connected in series. When a current that changes in intensity according to the vibration of the speaking sound is transmitted from the microphone, the magnet The attraction to the diaphragm changes in strength, causing the diaphragm to vibrate and form sound waves in the air, and you can hear the other party speaking.

electrical signal acoustic signal

2. The principle of telephone

When speaking, the vocal cords vibrate and produce sound → causing the air in the medium to vibrate → the air vibrating causing the carbon particles in the microphone to become loose and tight → causing the resistance in the circuit to become large and small → causing the current in the circuit to become large and small → in another section, the magnet The attraction to the diaphragm changes in strength due to changes in current → causing the diaphragm of the earpiece to vibrate → forming sound waves in the air → air vibrations causing the eardrum to vibrate → hearing the speaker’s voice.

Working principle: The microphone turns the acoustic signal into a changing current. The current transmits the information to the distance along the wire. In another section, the current vibrates the diaphragm of the earpiece, and the current carrying the information becomes sound again.

think about it

In fact, after the call is connected, the handset and the other party's microphone are connected in series in the same circuit through the relevant equipment of the telecommunications office. The reason is that the current in the series circuit is equal everywhere, and the handset and the other party's microphone can be connected in series to ensure that the current intensity changes between them. Consistent, so that the vibrations of the thin iron piece of the earpiece and the diaphragm in the other party's microphone are consistent, ensuring that the sound heard is the same as the other party's speech.

telephone exchange

Principle: All calls in an area are connected to the same switch. Each phone is assigned a number (i.e. phone number). When connected to the switch for use, the intercourse machine connects the two phones that need to talk, and disconnects the line after the call is completed. open.

If several pairs of telephone lines are connected between one switch and another switch, users of two different switches can talk to each other.

3. Actual telephone

1. In addition to the receiver and microphone, the actual telephone also has a bell, dialing equipment, etc.

2. Modern telephones include: wireless telephones, video telephones, recording telephones, etc.

analog signal

Analog signal: When the microphone converts sound into signal current, the frequency and amplitude changes of this signal current are exactly the same as the frequency and amplitude changes of the sound, "imitating" the "every move" of the sound signal. The signal transmitted by this current is called an analog signal, and the communication method using analog signals is called analog communication.

Features: During long-distance transmission and multiple processing and amplification of analog signals, the waveform of the signal current will change, causing the signal to lose some information, manifesting as distortion of sound and images, and in severe cases, communication interruption.

Digital signal

Digital signal: A signal represented by different combinations of different symbols is called a digital signal. This method of communication is called digital communication.

Features: Usually digital signals only contain two different states and are simple in form, so their anti-interference ability is particularly strong. Digital signals can also be encrypted using different encodings.

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Update Time: 2024-07-26

This template belongs to Physics courseware People's Education Edition Ninth Grade Physics Complete Book industry PPT template

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