The principle of telephone transmission

Call principle, that is, dialing principle.

At present, the basic dialing method is DTMF (early pulse dialing). Dual-tone multi-frequency refers to DTMF (Dual-tone multi-frequency), and DTMF signals are composed of eight frequencies.

These eight frequencies are divided into two groups: low frequency group and high frequency group.

When the "calling party" sends the DTMF signal dialed off-hook to the program-controlled exchange of this bureau through the telephone line.

Through program-controlled exchange, it is transmitted from telephone line to telephone, realizing the conversation between the two parties.

The answer principle, that is, the call principle.

Conversation is a kind of communication technology that uses electricity as the medium and transmits language through the mutual conversion of acoustic energy and electric energy.

When the "calling party" picks up the phone and speaks into the microphone, the vibration of the vocal cords excites the air to vibrate, forming sound waves.

Sound waves act on the microphone to generate current, which is called speech current.

The voice current is transmitted to the program-controlled exchange along the line, and the program-controlled exchange transmits the voice signal to the receiver of the "called party" phone, which plays the opposite role to the microphone-converting the current into sound waves and transmitting them to people's ears through the air.

The simplest call process is completed.