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A wireless microphone, or cordless microphone, is a microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated. Also known as a radio microphone , it has a small, battery-powered radio transmitter in the microphone body, which transmits the audio signal from the ...
Applications for short-range wireless devices include power meters and other remote instrumentation, RFID applications, radio-controlled models, fire, security and social alarms, vehicle radars, wireless microphones and earphones, traffic signs and signals (including control signals), remote garage door openers and car keys, barcode readers ...
Bluetooth devices intended for use in short-range personal area networks operate from 2.4 to 2.4835 GHz. To reduce interference with other protocols that use the 2.45 GHz band, the Bluetooth protocol divides the band into 80 channels (numbered from 0 to 79, each 1 MHz wide) and changes channels up to 1600 times per second.
Litke’s wireless mike resembled a silver tube with “a microphone at the top, a transmitter in the middle and its battery power supply at the bottom.” [1] It was 6 inches long, 1 inch in diameter, and weighed 7 ounces; the device had a broadcast range of up to a half-mile. Two types of mikes were available: lavalier and hand-held.
A wireless microphone with a non-diversity receiver (a receiver having only one antenna) is prone to random drop-outs, fades, noise, or other interference, especially if the transmitter (the wireless microphone) is in motion. A wireless microphone or sound system using diversity reception will switch to the other antenna within microseconds if ...
In free space the intensity of electromagnetic radiation decreases with distance by the inverse square law, because the same amount of power spreads over an area proportional to the square of distance from the source. The free-space loss increases with the distance between the antennas and decreases with the wavelength of the radio waves due to ...
In the UK, the use of wireless microphone systems requires a Wireless Telegraphy Act license, except for the license-free bands of 173.8–175.0 MHz and 863–865 MHz. These license-free bands are sometimes referred to as "Channel 70" (not to be confused with TV Channel 69, which operated on 854–862 MHz and always required a license from JFMG ...
In telecommunications, [1] particularly in radio frequency engineering, signal strength refers to the transmitter power output as received by a reference antenna at a distance from the transmitting antenna. High-powered transmissions, such as those used in broadcasting, are expressed in dB-millivolts per metre (dBmV/m).