Development History Of Bluetooth Headset

The first peripheral to use Bluetooth technology will be a wireless headset. According to Ericsson's schedule, this headset for Ericsson T28 phones was launched in July 2000. The corresponding products of Nokia and Motorola will wait until late 2000. At that time, as long as you add an accessory using Bluetooth technology to your mobile phone and place the headset in your ear, you can put your mobile phone in your pocket, free your hands during a call, and even press a button on the headset to answer the call. Moreover, because Ericsson T28 has voice recognition function, you can make some commonly used calls by simply saying the name of the person. Another selling point of the headset is that since the emission level of the Bluetooth headset is far lower than that of the ordinary mobile phone headset, the manufacturer will have the opportunity to highlight its advantages to human health.

However, the positioning of Bluetooth is low-power, short-range wireless transmission, and there is still a huge application space in the future consumer electronics. It will take personal portable products such as mobile phones and PDAs as its largest application market. According to in stat's estimation, by 2005, mobile phones will account for 71% of all Bluetooth application products, followed by personal computers and PC cards, accounting for 14%, and earphones, accounting for 6%. Analysts pointed out that with the progress of Bluetooth technology and the reduction of chip set cost, Bluetooth and Wi Fi will still account for half of the short-range wireless communication market.

Compared with the special miniature invisible wireless earphones, the civil and industrial wireless earphones can be described as various and varied. However, in fact, this kind of earphones is not very special in terms of communication and electronics, and it is more likely to involve the discussion in the field of acoustics.

The whole system of such earphones can be analyzed with reference to the low-power simplex or duplex radio communication system. In general, it pays attention to the fidelity of the restored sound quality, and the appearance is beautiful and attractive; In contrast, industrial wireless earphones are designed with more emphasis on reliability due to environmental reasons.

In the circuit, the processing mode of the transmission process of higher-grade products generally integrates analog or digital compression technology, and the modulation modes adopted are also various, such as RF, infrared, pure audio induction, etc. The varieties adopting RF mode and products using ultra-high band or Bluetooth Technology (900mhz-2.4ghz, etc.) can relatively achieve more ideal technical indicators and meet the requirements of green environmental protection, which actually represents an important development direction in this field.

The full duplex wireless headset for radio and television broadcasting adopts the FSK audio digital compression decompression modulation processing technology with low power consumption, and has high recovery index and anti-interference performance in the range of 20Hz-20KHz of human audible audio. The whole works in the UHF band of 863mhz. The PLL phase-locked loop makes it have stable radio frequency performance. In general, the reliable communication distance is more than 150m.

In general, in order to achieve an ideal high-speed digital speech compression transmission effect, a large RF bandwidth or advanced modulation technology is generally required. In order to reduce the rate of transmitting digital speech signals, adaptive audio pulse coding (ADPCM) or continuous variable slope delta modulation (CVSD) are often used to process the signals. These schemes are based on differential coding. The basic concept is to send the difference between the current sample and the previous sample instead of the absolute value obtained by sending the sample.

Wireless earphones will be used in many occasions. In addition to radio and television systems, such as call center, audio-visual teaching, home hifi, hands-free communication personal mobile phone (Bluetooth earphone), "silent meeting", interview and investigation, tourism and other wireless earphone systems can show their charm and are gradually becoming a trend. In fact, there is not much difference in the basic structure or circuit principle between various wireless earphones, nor is it necessary to strictly divide them into several categories. On the contrary, many earphones are used in a wide range of industries. When it comes to the difference, it is only for different applications. The parameters and costs of the system have a certain trade-off bias, which is the same as the requirements of the dedicated micro wireless earphone system.