alarm
attention
big
brother
cam
camera
cctv
ceiling
control
crime
danger
digital
electronic
equipment
guard
illustration
isolated
lens
look
monitoring
observation
observe
observer
optical
police
privacy
private
property
protect
protection
recording
safety
secrecy
secret
secure
security
set
sign
spy
street
surveillance
symbol
system
technology
video
view
watching
white