radar, radio detection and location, RADAL

detector, locator

to use / to employ / to make use of, to apply / to spend

search, look for

metal detector

radio wave / mobile phone signal / (slang) nonsense produced by a mentally unsound person, who is termed a 電波(でんぱ)系(けい) (denpa-kei, “radio-wave-type”) person

(slang) random and nonsensical

detection / discovery

detect / discover, uncover

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend