The Anchor Audio PRO-540/4S is a digital wireless intercom system that is easy to configure and easy to operate. The system allows duplex communication by four users with a master belt pack and three remote belt packs. It has a 500 ft. line of sight range and a built-in Bluetooth capability. The transmitter and receiver operate in the FCC license free 902-928 MHz range for the U.S. without the need for a base station. The ergonomically designed belt packs have a sturdy XLR headset jack, two heavy duty antennas, headset volume control, microphone gain control, A/B channel selection and PTT or Always On mode. The out of Range LED indicator tells each user when to move closer to the master belt pack. A gang charger is available to charge up to four belt packs on one device.