[Stooky Bill]

How does the 18:58 switch of CBBC/BBC Three and CBeebies/BBC Four work? What actually goes on in the automation, why did it go wrong when the channels launched in 2002 and what did they do to circumvent it? I remember reading that there was an early closedown on CBBC & CBeebies but that's about it.

Its basically a reconfiguration of the platforms that the channels broadcast on so that the video stops going out on one channel number and reappears on another. AIUI they just change the ID numbers and names of the services in the DVB stream.

In terms of what happens to the channel itself, at 1858ish it fades to black and then at 1900ish the new channel starts

It's automatic and happens twice a day on every version of the BBCs multiplexes - so each region of PSB1 and 3 and on satellite. There are other daily config changes, for example In Scotland and Wales channels like Alba and S4C are switched on and off. Engineers on duty check that these happen correctly

No idea why it went wrong in the early days, presumably just because it was new and they were still learning. It's a totally different set up now though