the value of old test and repair equipment

Eric Smith spacewar at
Wed Aug 10 11:16:18 CDT 2016

On Tue, Aug 9, 2016 at 10:31 PM, tony duell <ard at> wrote:
> The problem is that one of the 300 baud Bell tones is effectively the
> same as (I think) the long-distance clearing signal. Something like that
> anyway. If you connect your 300 baud US modem over here it will
> effectively cause the exchange to hang up.

Wow, I knew the tones were different, but I thought that was just the
typical NIH syndrome, doing it different to be different.

CCITT (later ITU-T) V.21 (300 bps full duplex), V.23 (1200 bps
half-duplex) and V.22 (1200 bps full-duplex) modem protocols were
never popular in the US; Bell 103, 202, and 212, respectively, were
used instead.

So what did people do if they needed to make a data call to the US?
Was that just not done until the US started using CCITT modem
protocols such as V.22bis (2400 bps)?

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