Telephone dialing principle

Let's start with a funny situation. You can switch the phone to dual tone dialing mode (with P/T) and beep into the microphone. If the frequency is appropriate and accurate, you can call.

Of course, this is a theory, and it is difficult to completely imitate people's mouths.

When you dial, the phone will send out a double tone or pulse signal. For example, if you dial an 8-digit telephone number, there is actually a certain time interval between the signals it sends. For example, it is a pulse. After receiving these 8 pulses with price, the remote host will start the communication function between you and the target mobile phone according to the prior agreement, including addressing first, then ringing, then the other party will confirm and then connect.

Generally speaking, the telephone to the host of SPC exchange is not digital because it is directly connected by telephone line, but if there is an optical cable between the two offices because of the long distance, there will be a special process to convert these into digital signals. I'm talking about the past, and now it may be more advanced.

Generally speaking, under 1, the telephone does not convert the dialing audio into digital signals and send them to the remote computer for dialing, but the audio electrical signals directly communicate with the remote program-controlled exchange.

Usually you don't dial the right frequency because the number is very long, and the telephone number is at least 7 digits like 5 million, so it is difficult for you to make the right sound and your mouth is not like it.

In addition, you can do an experiment: record the sound when you dial the phone with a good sound quality MP3, and then play it into the microphone. See if you can dial.