Shure UT-883 Professional Wireless Microphone System

The UT - 883 is a professional quality wireless Clip Microphone with UT -
883 frequency and 50 to 100 meters range. This wireless microphone
system is suitable for public speaking and singing, it can also be used
on public address systems, Guitar, trumpet, saxophone. Also can be used
on Video Camera. It comes with a rechargeable receiver and a body pack
transmitter that has volume control. - Frequency Response: Extremely low
distortion - Fully Eliminate the interference signal - High receptive
antenna, Beautiful and practical - Battery signal - Operating distance :
50 to 100 Meters It comes with a rechargeable receiver, body pack
transmitter, tie-clip Mic, charger cable, battery and owners manual. 

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 microphone by radio waves to
a nearby receiver unit, which recovers the audio. The other audio
equipment is connected to the receiver unit by cable. In one type the
transmitter is contained within the handheld microphone body. In another
type the transmitter is contained within a separate unit called a
“bodypack”, usually clipped to the user's belt or concealed under his
clothes. The bodypack is connected by wire to a "lavalier microphone" or
"lav" (a small microphone clipped to the user's lapel), a headset or
earset microphone, or another wired microphone. Most bodypack designs
also support a wired instrument connection (e.g., to a guitar). Wireless
microphones are widely used in the entertainment industry, television broadcasting, and public speaking to
allow public speakers, interviewers, performers, and entertainers to
move about freely while using a microphone without requiring a cable
attached to the microphone.

Wireless microphones usually use the VHF or UHF frequency
bands since they allow the transmitter to use a small unobtrusive
antenna. Cheap units use a fixed frequency but most units allow a choice
of several frequency channels, in case of interference on a channel or to allow the use of multiple microphones at the same time. FM modulation is usually used, although some models use digital modulation to
prevent unauthorized reception by scanner radio receivers; these
operate in the 900 MHz, 2.4 GHz or 6 GHz ISM bands. Some models use antenna diversity (two antennas) to prevent nulls from interrupting transmission as the performer moves around. A few low cost (or specialist) models use infrared light, although these require a direct line of sight between microphone and receiver.