Nady EO3 Wireless Personal In-Ear Monitor System with Earbud Headphones Ultra-compact design with an operating range of 300-feet and up to 130dB for in-ear monitoring. Ideal for both small and large venues. Operates at an uninterrupted frequency range which provides stability and maximum compatibility with other close-range UHF/VHF wireless systems. Compatible with professional in-ear monitor earbuds and consumer headphones with 3.5mm jack Any number of EO3 receivers can be used with a single EO3-T transmitter. Serving perfectly for not only live music performance but also event coordination, staff direction, and security communication relay.