The musical doorbell consists of a speaker, several electronic components and dry batteries. Among the electronic components, there is a semiconductor integrated circuit called a "music generator", which is the "heart" of the music doorbell. In the music generator, there is a part of the circuit called the oscillator, which is used to generate electrical vibration; there is also a part of the circuit called the "beat generator".

The music emitted by the doorbell is programmed in advance by a computer, and an electrical signal is recorded in a circuit called a memory in a part of the music generator. After pressing the doorbell switch and turning on the battery power, the electrical signal in the memory can direct the oscillator and beat generator to work in an orderly manner, so beautiful music comes from the doorbell.

In the music generator, there is also a part of the circuit called the tone generator, which is responsible for decomposing the electrical vibration generated by the oscillator into various tones such as "Duo", "Lai", "Mi", etc. The beat generator can provide 8 different beats and certain pauses for the tones generated by the tone generator.

"Doorbells" often appear in ancient foreign movies, and most of them are wealthy households hanging a huge bronze handle in front of their door. When the coachman delivers the guests to the door, he will pull the bell inside to indicate the arrival. In modern times, "doorbells" are no longer just for wealthy people. "Doorbells" have been widely used in ordinary people's homes. Various kinds of "doorbells" abound, and the function of "doorbells" is not limited to calling guests.

In the first two years when the author was interested in "doorbells", I collected many new "doorbell" circuits, made several self-made "doorbells" with different sounds, and also made many extensions. The tests on the function of the "doorbell" are all very practical.

The most common "doorbells" among modern citizens are electronic ones:

The most common ones are the "electronic doorbells" that were popular in the past few years; usually two AA batteries are installed Inside, after someone presses the trigger button outside the door, the "doorbell" inside the door will beep a few times. Some also use IC chips to play a piece of electronic music.

Later it evolved to the point where the guest could speak to the host of the house upstairs at the door, and the host would open the door to the guest after verifying his true voice. Their disadvantage is that they consume power. Especially those using batteries have more problems, but those using AC are afraid of temporary power outages.

The "doorbell" in a high-end apartment is the most expensive of its kind. Not only can it call the door to talk, but it can also use the camera to let the owner of the home see the guests far outside the door and downstairs on the screen. It would be a good idea to use such a "doorbell" to monitor the vehicles placed downstairs.