DESCENT T2

The Garmin Descent T2 is a transceiver rather than a transmitter, and that difference is what lets it carry messages as well as tank pressure. It both sends and receives over SubWave sonar, so a cylinder pressure and a preset message from a buddy travel the same acoustic link through water.

The T2 is rated to 200 metres and 300 bar working pressure on a 7/16 inch 20 UNF thread, and runs up to 100 hours of diving. It transmits at 2.4 gigahertz. Tank pressure reaches the paired computer at up to 10 metres, and diver-to-diver messaging reaches 30 metres with a compatible Descent Mk3i. Operating range is minus 20 to 60 degrees Celsius in air and 0 to 40 degrees in water.

The result is a dive team that sees each other's gas. A compatible computer reads up to eight cylinders, so a guide watches the group's pressure without asking for hand signals, and a low-gas diver shows up before the signal comes. Messaging works only where both divers carry a T2 and a computer that supports it.

The T2 ships with an air spool and documentation and screws into a standard first-stage high-pressure port. It pairs with the Descent Mk3i, the Descent X50i and the Descent S1 Buoy. Divers on a Descent Mk2i need the earlier Descent T1, which is rated to 110 metres and carries pressure only.