HSP、HFP、A2DP
    As for choosing Bluetooth earphones, the most troublesome issue for consumers is the compatibility between the phone and Bluetooth earphones, as there are many brands of phones and earphones. The manufacturer pointed out that Bluetooth earphones have HeadsetPro file (HSP) specifications
    HSP provides the basic functions required for communication between mobile phones and headphones in three specifications: HandfreeProfile (HFP) and A2DP. HandfreeProfile
    HFP has added certain extension functions on the basis of HeadsetPro file (HSP), which was originally only used to control mobile phones by fixing the car hands-free device with Bluetooth earphones. A2DP (Advanced Audio Distribution Specification) - allows transmission of stereo audio signals. Compared to mono encryption used for HSP and HFP, the quality is much better. Determine the compatibility between headphones and mobile phones. The HFP format Bluetooth earphones support a relatively complete range of mobile phone functions, and consumers can simultaneously operate hands-free options such as redial, call retention, and call rejection set by their phone on the earphones.
    Taking Bluetooth earphones launched by major manufacturers such as Nokia, Motorola, Sony Ericsson, and Jebre as an example, almost all of them mainly support HFP format. QCY and Pimet Bluetooth earphone models support both HFP and HSP, so consumers should pay special attention when purchasing.
    In addition, when consumers purchase blue goods, they often encounter the problem of how to choose the Bluetooth technology version. Different Bluetooth versions are related to the quality of the received signal, and the new version emphasizes the ability to overcome noise interference. Moreover, all the latest versions of Bluetooth are designed to be backward compatible with all previous versions. 2.0 devices and 1.1 versions can also be freely connected, and 3.0 has strong compatibility, which is a relatively mature technology. Bluetooth 4.0 is also compatible with higher versions and lower versions, and the battery life has increased due to technical prompts. Consumers should weigh the price and demand when purchasing.
    The distance of using Bluetooth earphones: not only depends on the earphones
    Another important factor for Bluetooth earphones is the transmission distance, which is not related to the Bluetooth version, but depends on the Bluetooth technology PowerClass. Most mobile phones and devices use
    PowerClass2, standard transmission distance of 10 meters: while the upgraded     PowerClass1 increases the transmission distance to 100 meters, both versions support A2DP stereo transmission protocol and can be connected to stereo headphones. Generally speaking, the distance between a mobile phone and a     Bluetooth headset is not too far. If there are no large obstacles in between, the transmission quality is good within 7 meters. If it exceeds 8 meters, there will be a breakpoint, and if it exceeds 10 meters, the connection between Bluetooth devices will be lost.