(UK) are the black boxes sensors or cameras on traffic lights?

i was just wondering what is the difference between cameras and sensors...because on some traffic lights they have numerous black boxes(UK) are the black boxes sensors or cameras on traffic lights?
If it's a camera it will have a visible lens. Otherwise its either a wiring junction box or a microwave sensor to detect presence of vehicles/pedestrians(UK) are the black boxes sensors or cameras on traffic lights?
light/movement sensors...next time, at night ,when your travelling towards a red traffic light flash your high beam...the lights will change to green in around 5 seconds cos its seen your lights flash....try it.



EDT..you seen the thumbs downs? ,thems from fools who know nowt...lmao....