These series products adopt UHF frequency and use the international standard common frequency which can be used in all over the world. Due to the low frequency and many reasons, traditional wireless microphone usually disturbed by many factors especially by the variety of harmonic which send off by CD/VCD/LD and other digital equipments. Squelch circuit usually analysis the intensity of the RF frequency channels instead of the noise and the needed signal. Using the low traditional wireless microphone in the complex environment or when the signal of the microphone is weak or the microphone is closured, the squelch circuit may suddenly opened which result the receiver send out a strong burst of noise. Do not change the frequency when using one set system. Using more than one set system in the same time, make sure the transmitter and the receiver of each system have the same frequency channel. Using many transmitter or receiver in the same room,choosing the best frequency channel is recommended.