The Bluetooth standard is divided into different standards:
IEEE 802.15.1 standard defines the Bluetooth 1.x to obtain a flow rate of 1 Mbit / s;
IEEE 802.15.2 provides recommendations for the use of the frequency band 2.4 GHz (frequency used also by the Wi-Fi). This standard is not yet validated;
The basic elements of a Bluetooth product are defined in the first two protocol layers, the radio layer and baseband layer. These layers support the physical tasks such as controlling the frequency hopping and clock synchronization.
The radio layer (the lowest layer) is managed in hardware.
It is she who handles the transmission and reception of radio waves.
It defines characteristics such as frequency band and channel arrangement, the characteristics of the transmitter, modulation, receiver, etc..
The Bluetooth system operates in the frequency bands * ISM (Industrial, Scientific and Medical) 2.4 GHz whose operation does not require a license. This frequency band is between 2 400 and 2 483.5 MHz.
A transceiver for frequency hopping is used to limit interference and mitigation.
Two modulations are defined: a compulsory modulation uses a binary frequency modulation to minimize the complexity of the issuer, an optional module uses a phase modulation (PSK symbols at 4 and 8). The modulation rate is 1 Mbaud for all modulations. The transmission uses a time division duplex.
The 79 RF channels are numbered from 0 to 78 and separated by 1 MHz, starting with 2402 MHz.
The information coding is done by frequency hopping. The period is 625 microseconds, allowing 1600 hops per second.
A loudspeaker is an electromechanical transducer for producing sound from an electrical signal. It is this contrast of the microphone.
By extension, it sometimes uses this term to a complete device for sound reproduction (see Article speaker).
There are many types of speakers:
representing the most common technologies actuellesles. The electrodynamic loudspeaker, covering about 99% of the market still has a relatively simple operation for a technology of mass.
The speaker is an invention already centenary. On December 10, 1877, the first patent for a loudspeaker voice coil was granted to Siemens CH. Today, the speaker performs a very wide range of applications: there are speakers in both greeting cards that related to power amplifiers for concert.
It operates on the following principle:
1.A motor converts electrical energy into mechanical energy;
2.This engine transmits the mechanical energy to the membrane;
3.la membrane transmits mechanical energy to the surrounding air - hence the sound.
Nowaday, speakers use also the bluetooth technology, who permit to avoid the usage of wires connection.
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