Protos have set the next milestone in the field of occupational safety. With the wireless Protos BT-COM, the most innovative head protection is now complimented with another ground-breaking feature. The Protos BT-COM technology provides, even under extreme use, stable and interference-free communication.Advanced Bluetooth wireless technology allows the connection of 4 BT-COM communication units, providing uninterrupted intercom connection between up to 4 operators. Protos Integral helmet not includedIncludes: One Protos BT-COM unit (left side). One Protos BT-COM Charging Bracket c/w USB connector One Protos BT-COM Carry Case for storage Specifications: Bluetooth Version - 4.2 Noise attenuation of up to 26 dB USB charging port - 5V DC, 200 mA, reverse polarity protected Lithium ion / polymer battery - 3.75V 600mAh Speaker output power - 0.2 Watt