Now ISDN over AMI I have seen (BRI) and done. It was a while ago,
and the loop length limitations are very short.
>From a user's point of view, they are full duplex. Full duplex
means that
you have a separate transmit path and a separate receive path. You can't
buy just a T1 receive-only or a T1 transmit-only pair, nor could you use
such a thing if you did (since FDL wouldn't work right), so it's
not quite
the same as two completely separate simplex links.
Newton's Telecom Dictionary (10th edition) defines Full-Duplex as
Transmission in two directions simultaneously, or, more
technically, bidirectional, simultaneous two-way
communications.
Simplex
Operating a channel in one direction only with no ability
to operate in the other direction.
So, the fact is that they ARE simplex links. This is also
documented in my course material received in the Hill Associates
course DataComm/2000.
>The point is that there are folks out there who think that a T1 is
a *total*
of 1.536Mbps user data (well, some think it's 1.544, but that's another
story entirely). It's not. It's 1.536Mbps each direction. All
the time.
OK, it's 1.536 Mbps USER data, but the ACTUAL line speed is 1.544
Mbps. 24 timeslots * 8 bits for each timeslot + 1 framing bit =
193bits now do this 8000 times a second and you get 1.544 Mbps.
Kyle Platts
CSS-Tech
!NTERPRISE Networking Services