There 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 the CD/DVD/VCD/LD and other any digital equipments. Squelch circuit usually analysis the intensity of the RF frequency channel 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 week or the microphone is closured, the squelch circuit many 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 transmitters or receivers in the same time, choosing the best frequency channel is recommended.