US military hardware does not use screw terminal blocks (at least what I have worked on).
At first I sorta thought it might be a jack; so J1.
I don’t really think of it as a “terminal”, it’s not the way I have seen “terminal” used in the field.
It would make sense that a terminal block, and a screw terminal block, would not share the same Ref Des. A terminal block typically connects two wire ends to the same terminal, while a screw terminal typically connects a single wire to a Pcb.
Yes, I have looked, Google is not helping me out at the moment. Anyone have some insight?
" From ANSI/IEEE 315 clause 22.4 the class designation of a terminal block is “TB” . . . . "
" Reference designation (letter symbol) for a terminal block is simply TB, such as TB6, and its terminals are treated just like connector contacts, such as TB6-3 . . . . "
and I will let you do the scholarship to verify the original sources.
(This tracks with my personal practice, but I didn’t know if there was an authoritative basis for my habit.)