This item make the sound around the microphone into the FM radio, and transmit out to achieve and wireless radio FM transmitter, the launch frequency is adjustable, the core board green components is the adjustable capacitor, change the adjustable capacitor can change Launch frequency, adjustable range covering 88-108MHZ GB FM-band.You can use the radio and the phone (the phone with the headset line to do the antenna sensitivity is poor, is not recommended as a receiver) as a receiver It is widely used in voice transmission, audio MIC, the elderly and children sleep monitoring, etc. need to the sound of the occasion Wiring : The back of the core panel is labeled +,- and ANT,representing the power positive,negative,and antenna ends.The antenna generally soldered a 0.7 meter long short wire on will be OK,which is easy Operating voltage: 0.7V-9VFrequency regulation range: 88-108MHZ (default 100MHz)Launch distance: 9V work, the use of 70 cm antenna, open space, launch distance of 50-100 The relationship between the operating voltage (volts) and the supply current (MA) and the transmitted power (dBm) is as follows:9V,24 Ma,9.5dBm7V,19 Ma,8.5dBm6V,17 Ma,7.1dBm5V,14 Ma,6.1dBm(about 5 MW)4V,12 Ma,4.5dBm3V,9 Ma,2.2dBm2V,6 Ma,-1dBm (about 1 MW)1.5V, 4.2 Ma, -4dBm (about 0.5 MW, general home environment emission enough, green radiation small)1V, 2.4 Ma, -9dBm0.7V, 0.9 Ma, -20dBm (. 0.01 MW)Condition:NewType:Voltage RegulatorModel Number:Diy Kit Electronic PCB Board ModuleApplication:ComputerSupply Voltage:100MHZcolor:Photo colorMaterial:plasticPackage Contents:1 x Transmitter ModuleOnly the above package content, other are not included.Note: Light reflection and different displays may cause the color of the item in the a little different from the real . The measurement allowed is +/- 1-3cm.