closed circuit; closed system
Technical term used in engineering and electronics to describe a circuit or system that forms a complete loop, as opposed to an open circuit. Often appears in compounds like 閉鎖式回路.
This device uses a closed-circuit cooling system.
semiclosed system
closed circuit rebreather
Compound of 閉鎖 (へいさ, 'closure') + 式 (しき, 'type' or 'system'). The derivation is straightforward from the kanji meanings.