EXMAX UHF-938 UHF Acoustic Transmission Wireless Headset Microphone Audio Tour Guide System 433MHz for Church Translation Teaching Travel Simultaneous Interpretation- 1 Transmitter and 10 Receivers This is a wireless headset system which could transmit the voice of person who speak to the microphone of transmitter to the people who wear earphone of the receiver,the transmission distance is about 50 meters(164 ft).The disadvantage is that you couldn't open two or more transmitters at the same place simultaneously, or they will disturb each other. To avoid this disturb, the distance of different transmitter should be at least 120 yards. This UHF-938 wireless system only have one channel, the frequency is 433 MHz, it has two input jacks, AUX and MIC, AUX is for external audio inputting, such as music playing from CD or MP3 player, MIC is for real-time human voice inputting,such as teaching, training, touring etc. You couldn't mix up the two jacks, or you will get noise.Since there is only one channel for this wireless system, the advantage is that it is very easy to operate. On each group,one transmitter can work with multiple receivers within the operating range.Low-power consumption design, 2pcs AA battery(NOT Included) can work more than 18 hours.The transmitter and receiver and headphones offer convenient, hands-free operation. Kindly note that This system requires a human language interpreter, it does not translate automatically. NOTE before Buying: Please DON'T buy many or large quantity sets/units one time if you never operated this system before or don't know what it is for. Strongly advise customers just 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.