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 pick up 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 very easy! Operating voltage: 0.7V-9V Frequency regulation range: 88-108MHZ (default 100MHz) Launch distance: 9V work, the use of 70 cm antenna, open space, launch distance of 50-100 meters The relationship between the operating voltage (volts) and the supply current (MA) and the transmitted power (dBm) is as follows: 9V,24 Ma,9.5dBm 7V,19 Ma,8.5dBm 6V,17 Ma,7.1dBm 5V,14 Ma,6.1dBm(about 5 MW) 4V,12 Ma,4.5dBm 3V,9 Ma,2.2dBm 2V,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, -9dBm 0.7V, 0.9 Ma, -20dBm (. 0.01 MW) Condition:New Type:Voltage Regulator Model Number:Diy Kit Electronic PCB Board Module Application:Computer Supply Voltage:100MHZ color:Photo color Material:plastic Package Contents: 1 x Transmitter Module Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.