UUCP `x' protocol

[Robert Heath]

For what type of network is the UUCP `x' protocol intended ?  
For example, `g' protocol is for TTY lines, `e' is for error-free LANs, and
`f' is for X.25 PAD's.  
I have heard that the UUCP `x' protocol is for use with the 
rather obscure Bell X.25 protocol but I can't seem to substantiate that
in my AT&T documentation.  Anyone got an idea on where `x' is used ?

	Robert Heath
	NCR Corp.
	E&M--Cola.