This Multi-Channel Wireless Headphone works with any Hamilton Wireless Headphone System or transmitter. These 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. Headphones operate for up to 40 hours and charge in only eight hours (LED indicator light lets you know when headphones are fully charged). Charge using Hamilton Wireless Multi-Channel Wireless Headphone System Transmitter.