Ceefax was the BBC’s broadcast teletext service that ran until 2012, providing text and rudimentary graphics that were broadcast invisibly with the TV signal. In order to get this teletext data merged into the analog TV signal, special equipment was needed, of which [Nathan Dane] has a 1997-era unit on his bench to take a gander at.

Interestingly, until this time the Ceefax signal had been generated centrally in London, meaning that regional TV broadcasts might have Ceefax issues on occasion due to retransmission glitches. This makes this Ceefax Inserter  system so much more interesting, as it was one of the early examples of what these regional stations would end up installing in their racks.

At their core these units are regular PCs, running MS-DOS 6.22 on a 486-class CPU and all the typical bits and bobs that go with a PC. The speculation here is that these are essentially rebranded industrial PCs, which would make a lot of sense. As for how [Nathan] got his hands on these units, it required a deal with the company scrapping them, preventing him from showing details of the software configuration.

Following a booting demonstration, we get the teardown of a typical 1990s rackmount PC, revealing a rather interesting backplane with the mainboard being one of the cards on it. Of these, two ISA cards provide the special Ceefax sauce as well as a timing signal in the form of a PDC card featuring a Lattice CPLD or FPGA that VCRs could use to automatically start recording.

The Ceefax main event comes in the form of the inSERT Teletext Encoder card. This is pretty much its own computer system, featuring a TI TMS34010 CPU and its own RAM as well as IO. Compared to modern takes on teletext generators, this card appears to directly mix the analog signals, without any kind of conversion.

Although teletext systems have been largely shutdown now at this point due to the transition to digital TV broadcasting, there’s still a lot to be said for having such a service available for basic news and information.