Recommend the latest ER-102 professional wireless monitoring system, it uses UHF signal transmission, has Bluetooth function, can connect multiple bodypack receivers for wireless monitoring, with high-fidelity HIFI headphones, used for recording studios, stage performances, classroom teaching, conferences speech, etc. The transmitter and antenna should kept in the relative position of accessibility of the straight line. Don't put the receiver close to the radio wave emission source, with magnetic objects or most digital devices(such as the CD player, computer, speaker, wifi etc). Try to place the receiver in height of 1.5 meters from the ground and the position of a distance of 1 meter away from the wall. Receiver Specifications: Frequency range:530-580MHz Signal transmission range: 300m (in an open environment) Receiving mode: Super heterodyne double-conversion Frequency vibration: PLL lock loop Sensitivity: -93 dBm Audio output: XLR balance output:0-500mV / ф6.35 unbalance output:0-500 mV Rated power consumption:3W Transmitter Specifications: Modulation Method:π/4-DQPSK Frequency Range:530-580MHz,1x100CHs (Please refer to the actual product for the frequency of some orders) Transmission power: 10mW Sampling Ratio:48KHz Transmission Rate:204.8Kbps Dynamic Range:Greater than 90dB Total Harmonic Distortion:Less than 0.1% Delay Time of Audio Transmission:Less than 3ms S/N Ratio:Greater than 96dB Frequency Response:30-20Khz RX Sensitivity:Less than -94dBm Color:Black Material:plastic Package Contents: 4 * receivers 1 * Transmitter