警防 is read as けいぼう (keibou) and means guard.
けいぼう
keibou
けいぼうだん
civil defense unit (Japan, 1939-1947)
けいさつちょう
National Police Agency
けいさつしょ
police station
(police officer's) baton
けいぶほ
assistant inspector
けいさつむせん
police radio
けいさつのぼうりょく
police violence
けいびへい
guard (soldier)
けいさつそうさ
police investigation
けいさつしょちょう
head of a police station
けいご
guard
こくぼう
national defence