- Engage 75 Mono includes headband and neckband- Allows 3X as many people to use the same headset compare to the older models- Advanced noise-cancelling microphone- Connect up to 5 devices (allow 2 USB devices, 2 Bluetooth device and 1 analog desk phone.- Speaker software separates noise from speech, reducing user stress- All incoming calls can be adjusted to a user-defined sound level that stays constant for all day comfort- Built-in busy light- Up to 13 hours of talk time- Up to 490 ft of range- 56-bit AES encryption. 128-bit authentication.- Battery replaceable