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There used to be a large telephone exchange in London called Baynard House, and this particular exchange has a rather interesting background which gives it something of a special place in the history of the Internet, modern telecommunications and the 1980s hacking scene. I started hacking electronics (including telephones) at a very young age, there was plenty of old hardware from the 80s turning up to investigate, and I had the pleasure of exploring a couple of circuit-switched telephone exchanges just after they were decommissioned around 1998. It’s a subject that warrants a blog post, I reckon.

System X
Baynard House was the first digitally-switched telephone exchange (at least in the UK), after System X was deployed there in 1980. Until fairly recently, the telephone network created a direct electrical circuit between the caller and receiver, through a series of relays. The relays themselves, which are still fairly easy to get hold of, had a circle of pins corresponding to the numbers on the old rotary phones, and latched as numbers were dialled. This was the circuit-switched network.

It was only after System X was deployed in 1980 that microprocessors gradually replaced the relay-based exchanges, and made possible ISDN and pulse dialling, and the Transmission Control Protocol was also being implemented around the same time. Together, these paved the way for dial-up Internet access in the UK. I think broadband Internet only existed after the circuit switched network was entirely phased out just over a decade ago.

Of course, it was intellectually very tempting to explore the country’s telecoms network, to control microprocessors at the exchanges by sending certain frequencies down the phone line, and to map out whatever’s installed there. Many people did just that, until out-of-band signalling and various security measures put an end to it, and that’s how proper hacking really took off. Hacking was about experimenting and knowing systems in depth, not the lame and pointless DDoS stuff that’s now considered ‘hacking’.

Prestel: The ‘Proto-Internet’
I managed to derive the following from ancient literature dating from 1983 and Wikipedia. Baynard House is where the Prestel service was based, housing a couple of mainframes subscribers around the country would dial into while using their television and a keyboard as terminals. There were several regional centres the data was mirrored to, but the majority of subscribers would have been the affluent who lived in central London. As far as I can determine, the Prestel service was closely related to the Internet, using dial-up modems and the same infrastructure, but data was sent in its entirety instead of as packets, and the routing was done at the telephone exchanges.

But this was before relay-based exchanges were phased out, so the subscribers had to dial the number and place the handset on the modem, and the modem would send whatever series of tones down the line to the mainframes at Baynard House. There was also something known as ‘telesoftware’, in which the reverse would happen, and programs were downloaded by recording tones issued by the Prestel mainframe. Perhaps this is partly the reason cassette tapes were used for storing programs.

From 1982, packet switching between Baynard House and other exchanges made Prestel accessible from the United States, although the end users themselves accessed the service over fixed routes. In that same year, the first Internet link between universities in the US and the UK was established, and I suspect the majority of the UK’s Internet traffic was being routed through Baynard House until the mid-1990s.

A Plantagenet HQ
The site also has some significance in medieval history. Along with a building owned by the Bank of New York, the exchange happens to occupy the site of a palace/castle destroyed in the Great Fire of London (1666). Several of the Plantagenet dynasty – Edward IV, Queen Mary and most notably Richard III – were crowned here, and it was also where the House of York were based during the War of the Roses.