Richard said:
Because it isn't true. I stand corrected .I never used real, old TTL but
only the LS and HC stuff as well as the 40xx series. I can't recall where I
got the idea that TTL had OC outputs in general. I was unsure enough of it,
however, to recommend checking the datasheets of the parts in question so at
least my post couldn't have done real harm.
robert