Professional wireless conference microphone system, UHF 620-678MHz frequency range, PLL Synthesized circuit, Four channels conference transmitters with the press to speaking button and speaking time on-screen display, base receiver for 4 pcs conference mics, download the frequency from the receiver by IR Sync, LCD status of frequency, AF and RF signal etc, Transmitter Power: 10~30mW, Battery Voltage: 3V (2x1.5V AA Battery), Continuous Using: 5 hours.