常闭开关 normally-closed switch

常闭和常开 NC&NO ; NCandNO

常闭/开 Normally off/on

常闭按钮开关 [电] normally closed push button switch

常闭或常开 d or

常开常闭型 Form ; COM NO NC

常开和常闭通用 Form

常闭铵钮开关 normally closed push button switch

常开常闭 NONC

以及常闭常开转换型 FORM