I had to Google (amusingly) to ensure I had my historical pedantic pet peeve correct (memories can fail us).
It was just 56k. I seem to recall back in the day people appended the ".6" for no apparent reason other than it sorta seemed logical after we had 14.4k, 28.8k, 33.6k, and then.. all of a sudden.. 56k.
(and, if I recall correctly, for technical reasons it was really only 52k, and even then, only if you were lucky, usually it was less.
I seem to recall that the equipment was theoretically capable of 56k but in actual implementation, even a perfect POTS system wouldn't do over 52k, and in the real world, it would usually negotiate lower due to distance from CO, quality and number of connections and equipment in between, etc).
It was just 56k. I seem to recall back in the day people appended the ".6" for no apparent reason other than it sorta seemed logical after we had 14.4k, 28.8k, 33.6k, and then.. all of a sudden.. 56k.
(and, if I recall correctly, for technical reasons it was really only 52k, and even then, only if you were lucky, usually it was less.
I seem to recall that the equipment was theoretically capable of 56k but in actual implementation, even a perfect POTS system wouldn't do over 52k, and in the real world, it would usually negotiate lower due to distance from CO, quality and number of connections and equipment in between, etc).