Feature: 1. The transmission frequency of the audio transmitter module can be adjusted, and the adjustable range covers 88‑108mhz national standard FM band. 2. The green component is a tunable capacitor, changing the tunable capacitor can change the transmit frequency. 3. With 0.7V‑9V wide voltage working range, long transmission distance, strong practicability. 4. You can use radios and mobile phones as receivers (the earphone cable for mobile phones makes the antenna sensitivity very poor and is not recommended). 5. Widely used in sound transmission pickups, audio microphones, sleep monitoring and other situations where sound needs to be captured. Specification: Item Type: Audio Transmitter Module Material: PCB Application: Widely used in sound transmission pickups, audio microphones, sleep monitoring of the elderly and children, etc. where sound needs to be captured Working Voltage: Ultra-wide 0.7V-9V Frequency Adjustment Range: Wider than 88-108MHZ Transmission Distance: When working at 9V, use 70cm wire as antenna, and the transmission distance is approx. 50-100meters / 164-328.1ft in an open area, depending on the actual environmentThe relationship between working voltage (volt) and supply current (milliamps) and emission power (dBm) is as follows: Working Voltage Supply Current Transmit Power 9V 24mA 10.2 dBm (about 11mW) 8V 21mA 9.5dBm 7V 19mA 8.5dBm 6V 17mA 7.1dBm 5V 14mA 6.1 dBm (about 5mW) 4V 12mA 4.5dBm 3V 9mA 2.2dBm 2V 6mA -1dBm (about 1mW) 1.5V 4.2mA -4dBm (approximately 0.5mW, emission in general home environment) 1V 2.4mA -9dBm 0.7V 0.9mA -20dBm (about 0.01mW) . Package List: 1 x Module