Howard, I have an internet connected system, which sends emails of 'events', it logs them on my computer and on the SD card in the camera itself. It must be connected to a working broadband router.
I can also logon to an app as have a live view when I am away from home.
At first I tended to review the footage and noticed some characters coming up the drive, clocking the CCTV camera and going. Life is too short for that.
We people come to the door they also clock the camera. I would say it can act as a deterrent.