This format was discussed in a HN first page post just this week:
> This alphabet, 0123456789ABCDEFGHJKMNPQRSTVWXYZ, is Douglas Crockford's Base32, chosen for human readability and being able to call it out over a phone if required.
> This alphabet, 0123456789ABCDEFGHJKMNPQRSTVWXYZ, is Douglas Crockford's Base32, chosen for human readability and being able to call it out over a phone if required.
Also 2 and Z can be similar in writing.
However it is nice to not see 0 and O, 1,I,l in the same string.
POTS = Plain old telephony service is restricted to a narrow frequency range of 300–3,300 Hz, called the voiceband, which is much less than the human hearing range of 20–20,000 Hz [from https://en.wikipedia.org/wiki/Plain_old_telephone_service ]
Fun fact: dzs counts as a single letter in Hungarian (e.g. in alphabetical ordering).