http://www.historic-newspapers.co.uk/Old-Newspapers/1930-Newspapers
ISBN check codes are designed to catch common errors back when hand entry was common -
a run of two digits in the wrong place (eg 556 instead of 566)
a mistyped digit
two digits swapped around by one place
The UPC code does not support the latter at the expense of only requiring the check symbol to be one of 10 regardless of the number of digits in the code. The ISBN algorithm requires n+1 where n is the number of data digits. Whether this is required nowadays given that very few ISBNs are entered by hand is another issue.
Except that electrons travel a fuckton slower than the speed of light through a wire. 66% through standard coaxial
Electrons travel a lot slower than that - although you are correct that that is the wave propagation speed in coax which is what really matters.
It's still faster than wave propagation in an optical fibre though.
It is still used in a lot of theatre installations in the UK. It means the only fuse/breaker to blow/trip is in the dimming rack not 20 feet up on an inaccessible lighting bar as might happen with BS1363. Also makes chained extensions far easier to deal with.
"Everything should be made as simple as possible, but not simpler." -- Albert Einstein