"Jim Wilkins" fired this volley in news:lr8l9p$sn5
:

Not long after he fried himself messing with the live 480V line

No... you mean the 48V line, don't you? 480 can't hurt you!

Actually, you can ground-short a TTL output and (attempt to) drive it
high -- for a while. There's some resistance in the high-side of the
totem pole. It'll source something like 50mils. But it's sure not good
for it (that'd be something like 1/4W per output!). And certainly not
more than one gate at a time in any given package.

And it's also not good for the base-emitter junction of the typical small
switching transistor! I think max base junction current on a 2N2222 is
something like 50 mils, too.

Lloyd