Davosa Watch Ternos Professional TT 16155995. The abbreviation TT is not unknown. A car bearing the same two letters stands for tradition and technology. This aspiration is easily fulfilled by the reworked Ternos Professional TT, it is water resistant to a depth of up to 500m , can automatically regulate gas pressure via a helium valve and a bicolour, rotatable bezel that now provides visual support for the 15 minute limit before resurfacing. This last feature is what really gives the Ternos Professional TT its name, Two Tone, in either blue black or grey black.