The Multi-Channel Wireless Headphone System Transmitter gives you an adaptable learning lab, because you can use an unlimited number of headphones (not included) on the same frequency. Cordless headphones function up to 100 feet away from the transmitter, so students can use them anywhere in your classroom. Simply turn the units on and use the channel selector under the leatherette ear cushions to choose a frequency. For use with Hamilton Wireless Headphones.