How do the freeview people disconnect top-up TV when they don't have access to your set top box?

Question

When I called to cancel my TUTV it was deactivated the same day, how is it done when there is no connection between the set top box and the service provider?

Answer 1

They send an extra signal on the same frequency as their TV transmissions, in the box is a coded unit, set to accept that signal, be it on or off to recieve Top Up.