The Multi-Channel Wireless Headphone System allows group training, because you can use an unlimited number of headphones on the same frequency. The cordless headphones function up to 100 feet away from the transmitter, so employees can use them anywhere in your office. 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 (transmitter doubles as charger; LED indicator light on headphones lets you know when they’re fully charged). Add a headphone rack for an additional cost.