Relay computerswhy so few 18

You might well have designed a PBX, but nobody designed an all digital switching fabric suitable for a 10,000 line CO switch until somewhere around 1975-6.

There is a *big* difference (routing between modules in the switching fabric, for example).

Designing your own non-compatible telephone system may have had certain advantages, but it also had some rather extreme disadvantages. In 1970 that wouldn't have been quite the problem it would become a decade later when FAX and data modems, not to mention the whole customer premise equipment market, became much more developed. (Such systems were common, but in the end only those that also provided standard interfaces as an installable option survived.)

But it must have been a really interesting experience! At the time it was a wide open field, and nobody had any idea where it was headed, though it was obvious that there would necessarily be some mbuttive changes. The Carterphone decision set the political-legal path, and the invention of integrated circuits upended every technical precident. Who would have thought it would lead to breaking up the Bell System in 1984, followed in another 20 years by essentially the dissolution of AT&T itself...

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