It would be a good idea to put a security light with a motiondetector in the garden.
Times, Sunday Times (2010)
An externally monitored security and CCTV system has been fitted, which includes motiondetectors, vibration sensors on windows and doors and a video door entry system.
Times, Sunday Times (2012)
As the marines came under attack, motiondetector alarms went off in security command post.
Times, Sunday Times (2012)
Definition of 'detector'
detector
(dɪtektəʳ)Explore 'detector' in the dictionary
countable noun [oft noun NOUN]
A detector is an instrument which is used to discover that something is present somewhere, or to measure how much of something there is.