This is the OTS MK-7 Buddy-Line Portable Two Diver Air Intercom 4 Wire The MK7 BuddyLine is a compact, self-contained one or two-diver air intercom. It will allow clear communications in the 4-wire mode (round robin) and includes the THB-7A Deluxe Headset (with boom mic). The MK-7 BuddyLine was specifically designed for Search & Rescue Teams to have an underwater communication device that needs little set-up time.The 2 watts of power is managed by state-of-the-art circuitry allowing relatively long life and great intelligibility. MK-7 BuddyLine operates on 8 AA alkaline batteries. The MK-7 BuddyLine and our ComRope is a great package that ensures a dive operation runs smoothly. mk7