Guardian Plus 4 users kit-ProAudio with MAE 410 Headset. Unlimited number of users. Intuitive handling, no fixed installation required. HD sound: 16 Khz audio sampling rate cryptage. Hardened digital encryption: exchanges secured by an AES 128 key. Hands-free system, instant and continuous communication. Patented noise filter, suppression of surrounding noise. Group function available. Alarm function: vibrator or audible signal. Bluetooth compatibility (phone and accessories).