Ceefax was a service that provided a series of pages of coloured text in a format similar to a 40-column display to a compatible television set. Each page was numbered, and you could address each page by its number. Typing in a number would bring up the relevant page with about the same latency as a dial-up modem.
This hasn't made sense to me since I knew how a television worked. The television can't transmit back to the transmission tower; even if it could, my aerial is much too small to send a signal that could reach the transmission tower without being drowned out by other signals from the transmission tower. Even if it was, there'd be interference from the other televisions' signals. And even if all of the signals managed to get to the transmission tower intact and there was the necessary infrastructure to process all of the signals, there'd be no way for the transmission tower to send an extremely directed signal to the specific aerial that transmitted to it... surely.
I am certain that there was not enough RAM in my old CRT to store all of the Ceefax pages whilst the television was in Standby mode (although it did seem to take a while for Ceefax to become available after power was given to the machine...), but I can't see any other ways that this could have worked.
How was Ceefax designed, implemented and transmitted?