1, earphone and microphone, that is, the wire input end of earphone has two plugs, which are signal input and signal output (microphone) respectively.
2. The earphone signal input is compatible with different specifications of equipment output jacks. The advantage is that one earphone can be connected to two types of jacks. Just insert the corresponding plug into the electrical jack and put the other plug into the spare plug box, and it can be conveniently used on any electrical appliance that needs headphones.
3, hybrid machinery, a machine has a variety of power input requirements, that is, a line with multiple plugs, which not only avoids line confusion, but also ensures the independent and simultaneous use of multi-functional requirements.
Extended data
Headphone plug, DC plug, audio plug, usb plug, video plug, microphone plug, electrical appliance plug, mobile phone plug, etc.
Internationally, household appliances are divided into three categories:
Class I: Electrical appliances refer to those with only one layer of insulation measures. This kind of electrical appliance must be equipped with leakage protector and grounding protection (that is, three-pin plug). Such as air conditioners, machine tools, motors, etc.
The second category: electrical appliances have double insulation measures, so it is necessary to add a leakage protector without grounding protection (that is, two-pin plugs can be used). Such as: TV, electric fan, desk lamp, induction cooker, ceramic electric stove, etc.
Category III: Electrical appliances are from safe voltage, generally 12-36V, such as mobile phones and notebook computers.
References:
Baidu encyclopedia-double insertion
References:
Baidu encyclopedia-plugin