EXMAX ATG-100T 195-230MHz Wireless Tour Guide Monitoring Voice Audio Transmission System+Aluminium Alloy Charge Case for Teaching Tour guides Conference Church Museum(1 Transmitters and 30 Receivers) The EXMAX wireless audio transmission system could transmit voice of who speak to the microphone of transmitter to the ones who wear earphone of receivers,transmission distance is about 50-60 meters (164-197ft).99 frequency channels on 195MHz-230MHz means it has 99 select IDs allow at least 40 groups to work simultaneously.Widely used for field trip,tour exhibit guides,sermon interpretation,work-study,conferences,translation,audio visual laboratory,events for church,family,restaurants,hajj... Transmitter weighs 56g and receiver weighs 46g,Small and light for carry or carriage.High S/N Ratio(90dB) ensure cleanest voice transmission. Long-Lasting Power,both transmitter and receivers are built-in 900mAh lithium upgraded battery to guarantee more than 18 hours working.One transmitter could pair up countless receivers as long as they are on the same frequency.Transmitter has 3.5mm input jack, it supports AUX( such as MP3, Smartphone,MP4,CD etc) and MIC (microphone )input. The wire of microphone and earphone has antenna function, please do unfold the wire of the microphone and earphone to enhance the voice signal transmission. On each group, transmitter and receivers should be set on the same frequency Channel ID,for example, Group A: transmitter A is set on Channel ID 05, so receivers A should be set on Channel ID 05 accordingly.But different groups should use different frequency Channel ID, so they will not interfere with each other when work simultaneously. NOTE before Buying: Please DO NOT buy many or large quantity sets/units one time if you never operated this system before or dont know what it is for . Strongly advise to buy one set/unit to test this system and completely understand its functions and know its advantages and disadvantages. If you like it after testing, you could buy many sets/units one time. Once a customer bought many sets/units of this system but immediately request returning right after he received the package due to he didnt like it and he realized that its not what he want. This raised too much costs and waste to the transaction, your kind understanding would be highly appreciated.