today I learned that DTMF is "dual tone" because each key generated one tone for the row it's in and one tone for the column that's a really... brute-force implementation, probably typical for 1963pic.twitter.com/vnDaxggVju
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I'm not from North America so the thing where only phone company equipment was allowed on the phone network was always really bizarre to me
In Germany there used to be a law that any device capable of producing DTMF tones had to have a TÜV certificate. So the CCC tuned a piano accordingly and used it dial some numbers, to demonstrate that all pianos need TÜV certificates according to that ridiculous law.
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Did they obtain a TÜV certificate for their piano?
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No. But there are a lot of obscure stories from that time. For ex, there was also a law that prevented you from electronically "picking up". So for operating a BBS you had to build a small robot to physically release the plunger (handset permanently in acoustic coupler).
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