In 1960, the new Salvas regulator, the Aquasprint, no longer had the annoying mechanical reserve mechanism on the tanks, replaced with a system that made breathing increasingly difficult from the moment the internal pressure dropped below 40 bar.
Almost thirty years later, when by now people were just keeping an eye on the pressure gauge to understand if it was time to start the ascent, the Italian company Gse trieste s.r.l. of Zingonia presented the SRV Tm which followed, albeit in a different way, the concept of the Aquasprint. Its purpose was to prevent people from forgetting to check the pressure gauge in time, risking suddenly running out of air.
The SRV Tm, applied to the hose just before the second stage, when the pressure in the cylinder dropped below 50 bar gradually increased the resistance to inhalation, giving a signal impossible to ignore. At that point it was enough to give half a turn to its knob to release the residual air, again breathable without effort until resurfacing.
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