regulator first stage
/ɹɪfjˈuːlɪŋ dɪvˈaɪs/
n
English · regulator first stage中文 · 一级减压器Español · regulador de la 1ª etapa de descompresiónFrançais · détendeur premier étage
意味：Apparatus attached to the cylinder valve that lowers the air pressure coming from the cylinder to an intermediate value (medium pressure).