1.This system comprises a set of automatic imput circuit of wireless microphone and a set of input unit of wired microphone and a set of input unit of Audio frequency signal. 2.Power supplies:2PIN AC jack,external DC jack ,8pcs1# battery compartment,rechargeable battery compartment.It depends on your requirments. 3.TREBLE/BASS is offered.the output of tone control can be microadjusted. 4.ECHO is offered. 5.Fixed stand is optional for installing the unit at higher position 6.USB/SD 7.LITHIUM bettery Right partner for sales promotion, top buddy of tour-guide lady, good instrument for meeting or get-together, excellent helper for outdoor or indoor teaching.