regulator second stage
/ˈɹɛɡjʊləɹ ˌɒktɐhˈiːdɹən/
n
English · regulator second stage中文 · 二级减压器Español · regulador de la 2ª etapa de descompresiónFrançais · détendeur second étage
意味：Apparatus that changes the pressure of the air coming from the regulator first stage to the pressure of the ambient air; the diver breathes this air in through a mouthpiece.